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1

Halogenated auxins affect microtubules and root elongation in Lactuca sativa  

NASA Technical Reports Server (NTRS)

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

Zhang, N.; Hasenstein, K. H.

2000-01-01

2

Stimulation of root elongation and curvature by calcium  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

3

Gibberellins accumulate in the elongating endodermal cells of Arabidopsis root  

E-print Network

Gibberellins accumulate in the elongating endodermal cells of Arabidopsis root Eilon Shania,1 , Roy be regulated. Gibberellins (GAs) are a class of tetracyclic diterpenoid hor- mones that regulate many levels (22, 23). Whereas molecules 1 and 4 had a very small effect on ga1 germination (4% and 8

Tsien, Roger Y.

4

The root cap and control of root elongation in Zea mays L. seedlings exposed to white light  

Microsoft Academic Search

Light-induced inhibition of the elongation of primary roots of Zea mays seedlings is dependent upon the perception of light by the root cap. Separate exposure of detached root caps and roots from which root caps have been removed (i.e. decapped roots) to white light or darkness has shown that the elongation of a dark-exposed root to which a light-exposed root

Henry Wilkins; R. L. Wain

1974-01-01

5

Effects of daylength and temperature on root elongation in tundra graminoids  

Microsoft Academic Search

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

G. R. Shaver; W. D. Billings

1977-01-01

6

Hyphal Elongation of Glomus fasciculatus in Response to Root Exudates †  

PubMed Central

The spore germination rates on water agar of the vesicular-arbuscular mycorrhizal fungus Glomus fasciculatus were highest at water potentials of ?4 to ?6 bars. Root exudates from plants grown in a sterile nutrient solution, with or without phosphorus, did not affect germination. Root exudates collected from 2-, 4-, and 6-week-old Trifolium repens cv. `Ladino' seedlings that were deprived of P enabled hyphal growth from germinated Glomus fasciculatus spores of 21.4, 14.7, and 7.6 mm, respectively. Hyphal elongation in the presence of exudates from plants grown with P, or in the absence of exudates, was negligible (<1 mm). Root P at 2 weeks was not significantly different between plants grown with and without P. There were no significant differences between the quantities of exudates from plants grown with or without P at 2, 4, and 6 weeks. The data suggest that it is the quality of exudates from plants experiencing P deprivation that is important in stimulating vesicular-arbuscular mycorrhizal hyphal elongation. PMID:16347418

Elias, Karol S.; Safir, Gene R.

1987-01-01

7

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

8

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

PubMed

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

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

2014-06-01

9

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

PubMed Central

The gain-of-function mutant edt1 shows significantly enhanced drought tolerance and a well-developed root system including deeper primary roots and more lateral roots. To explore the molecular mechanisms underlying the improved root system of edt1, we performed transcriptome comparison between the wild-type and edt1 roots. One of the interesting findings from the analysis was that several gene families of cell-wall-loosening proteins were upregulated in the mutant roots, including expansins, extensins, xyloglucan endotransglucosylase/hydrolases (XTHs), pectin-related enzymes, and cellulases. Most of these genes contain HD-binding cis-elements in their promoters predominantly with the TTTAATTT sequence, which can be bound by HDG11 in vitro and in vivo. The coordinated expression of these gene families overlaps fast root elongation. Furthermore, overexpression of AtEXPA5, which was dramatically upregulated in edt1, resulted in longer primary roots because cells were more extended longitudinally. When combined by crossing the AtEXPA5-overexpression lines with one pectin methylesterase inhibitor family protein (PMEI) gene (At5g62360)- or one cellulase (CEL) gene (At2g32990)-overexpression lines, the primary roots of the progeny even exceeded both parents in length. Our results demonstrate that HDG11 directly upregulates cell-wall-loosening protein genes, which is correlated with altered root system architecture, and confirm that cell-wall-loosening proteins play important roles in coordinating cell-wall extensibility with root development. The results of transgene experiments showed that expansin works together with PMEI and CEL to generate synergistic effects on primary root elongation, suggesting that different cell-wall-loosening protein families may function in combination to generate optimal effects on root extensibility. PMID:24821957

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

2014-01-01

10

Inhibitory Action of Auxin on Root Elongation Not Mediated by Ethylene  

PubMed Central

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

Eliasson, Lennart; Bertell, Gertrud; Bolander, Eva

1989-01-01

11

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

12

Role of cytoskeleton in gravisensing of the root elongation zone in Arabidopsis thaliana plants  

Microsoft Academic Search

In order to reveal the involvement of tubulin microtubules and actin microfilaments in gravisensing reactions in the distal elongation zone of root, Arabidopsis thaliana plants stably transformed with MAP4-GFP construct were grown under slow clinorotation. Experiments have shown that stabilization of cell growth in the distal elongation zone of Arabidopsis seedling root is provided by common structural organization of microtubules

G. Shevchenko; Ya. Kalinina; E. Kordyum

2008-01-01

13

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

PubMed

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

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

2014-04-01

14

Anatomical responses of root tips to boron deficiency I. Effects of boron deficiency on elongation of root tips and their morphological characteristics  

Microsoft Academic Search

Effects of boron deficiency on the elongation of root tips of tomato and sunflower seedlings were investigated and the morphological responses of root tips were discussed.The primary effect of boron deficiency was the rapid cessation of root elongation followed by browning and some morphological changes in the root tips, such as abnormal enlargement and dense appearance of lateral roots. Root

Hiroshi Kouchi; Kikuo Kumazawa

1975-01-01

15

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

PubMed Central

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

Moura, Daniel S.

2014-01-01

16

SWP1 negatively regulates lateral root initiation and elongation in Arabidopsis  

PubMed Central

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

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

2012-01-01

17

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

PubMed Central

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

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

1998-01-01

18

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

19

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. PMID:24121463

Hayashi, Kohma; Hasegawa, Junko; Matsunaga, Sachihiro

2013-01-01

20

An automatic image analyzing system for evaluation of elongating behavior of plant hairy roots exposed to herbicidal stimuli  

Microsoft Academic Search

The elongating behavior of pak-bung hairy roots was evaluated by automatic tracing of the root tip point employing computer-aided image analysis. Though the root elongation rate in the absence of herbicides was approximately constant, the addition of 1.0 pmol\\/dm3 2,4-dichlorophenoxyacetic acid (2,4-D) or pyributicarb to the culture led to gradual deterioration of the elongation rate during measurements over a 25

Kazuaki Ninomiya; Yuki Tsushima; Masahiro King-Oka; Masahito Taya

2003-01-01

21

Evidence That High Activity of Vacuolar Invertase Is Required for Cotton Fiber and Arabidopsis Root Elongation through Osmotic Dependent and Independent Pathways, Respectively1[C][W][OA  

PubMed Central

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

2010-01-01

22

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

NASA Technical Reports Server (NTRS)

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

Evans, Michael L.

1998-01-01

23

Metal-induced cell rupture in elongating roots is associated with metal ion binding strengths  

Microsoft Academic Search

Low concentrations of Al, Cu and La rapidly decrease root elongation and cause transverse ruptures to the rhizodermis and\\u000a outer cortex, but it is not known if other trace metals have similar effects. Six trace metals, Ga, Gd, Hg, In, Ru, and Sc,\\u000a decreased cowpea root growth and caused ruptures similar to those caused by Al, Cu and La. Calculated

P. M. Kopittke; B. A. McKenna; F. P. C. Blamey; J. B. Wehr; N. W. Menzies

2009-01-01

24

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

EPA Science Inventory

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

25

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

26

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

PubMed Central

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

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

2014-01-01

27

Role of cytoskeleton in gravisensing of the root elongation zone in Arabidopsis thaliana plants.  

PubMed

In order to reveal the involvement of tubulin microtubules and actin microfilaments in gravisensing reactions in the distal elongation zone of root, Arabidopsis thaliana plants stably transformed with MAP4-GFP construct were grown under slow clinorotation. Experiments have shown that stabilization of cell growth in the distal elongation zone of Arabidopsis seedling root is provided by common structural organization of microtubules and microfilaments, and interrelations between microtubules and microfilaments is highly dependent upon the type of cell differential growth. Less pronounced effect of microfilament disruption on microtubule organization has been observed under clinorotation and it suggests the existence of complex mechanism of cooperation between microtubules and microfilaments which is probably, masked on earth. PMID:18164634

Shevchenko, G; Kalinina, Ya; Kordyum, E

2008-05-01

28

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

SciTech Connect

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

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

1995-12-31

29

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

PubMed Central

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

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

2000-01-01

30

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

PubMed Central

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

2011-01-01

31

Role of Apoplastic and Cell-Wall Peroxidases on the Stimulation of Root Elongation by Ascorbate.  

PubMed Central

Elongation of onion (Allium cepa L.) roots was highly stimulated by ascorbate (ASC) and its natural precursor I-galactone-[gamma]-lactone (GL). When incubation media were supplemented with lycorine (Lyc), an inhibitor of the ASC biosynthesis, root growth was negligible even in the presence of ASC or GL. ASC completely inhibited in vitro guaiacol peroxidase activities that were isolated from both the apoplast and the cell wall. However, ferulic-acid-dependent peroxidase from the cell wall was partially inhibited by ASC, whereas ferulic acid peroxidase activity from the apoplastic fluid was completely inhibited by ASC as long as ASC was present in the assay medium. ASC content in cells was increased by preincubations with ASC or GL, whereas Lyc reduced it. On the other hand, ASC or GL treatments decreased both apoplast and cell-wall-bound peroxidase activities, whereas Lyc had a slight stimulating effect. These results are discussed on the basis of a possible control of root elongation by ASC via its action on peroxidases that are involved in the regulation of cell-wall extensibility. PMID:12226436

Cordoba-Pedregosa, MdC.; Gonzalez-Reyes, J. A.; Canadillas, MdS.; Navas, P.; Cordoba, F.

1996-01-01

32

How periodic growth pattern and source\\/sink relations affect root growth in oak tree seedlings  

Microsoft Academic Search

Seedlings of Quercus pubescens were grown in root boxes to study the growth pattern of the root system in relation to shoot development. Shoot growth was typically rhythmic. Root elongation was also periodic, in contrast to several previous reports on other Quercus species. Both taproot and lateral root elonga- tion were depressed during expansion of the second leaf flush, with

Magali Willaume; Loic Pages

2006-01-01

33

Interrelation between microtubules and microfilaments in the elongation zone of Arabidopsis root under clinorotation  

NASA Astrophysics Data System (ADS)

Arabidopsis thaliana plants stably transformed with a MAP4-GFP construct were grown under slow clinorotation to characterize the role of tubulin microtubules in cell growth and gravisensing in the distal elongation zone (DEZ) of the root. Plants were treated with actin and tubulin disrupting drugs to investigate the changes in microtubule distribution and orientation between clinostat grown and control plants. It has been shown that organization of microtubules in the meristem and DEZ of Arabidopsis seedling root is interrelated with the organization of microfilaments. Cooperation between cytoskeleton elements is dependent upon the type of cell differential growth and aimed to provide the stabilization of cell growth on earth. In contrast, under clinorotation the cross-talk between microtubules and microfilaments was less pronounced. This phenomenon suggests the existence of complex mechanism for regulation of microtubules and microfilaments which is probably, unmasked in simulated microgravity.

Shevchenko, G. V.; Kalinina, Ya. M.; Kordyum, E. L.

34

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. PMID:18703541

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

2008-01-01

35

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. PMID:18387193

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

36

Elongation and gravitropic responses of Arabidopsis roots are regulated by brassinolide and IAA.  

PubMed

Exogenously applied brassinolide (BL) increased both gravitropic curvature and length of primary roots of Arabidopsis at low concentration (10(-10) M), whereas at higher concentration, BL further increased gravitropic curvature while it inhibited primary root growth. BRI1-GFP plants possessing a high steady-state expression level of a brassinosteroid (BR) receptor kinase rendered the plant's responses to gravity and root growth more sensitive, while BR-insensitive mutants, bri1-301 and bak1, delayed root growth and reduced their response to the gravitropic stimulus. The stimulatory effect of BL on the root gravitropic curvature was also enhanced in auxin transport mutants, aux1-7 and pin2, relative to wild-type plants, and increasing concentration of auxin attenuated BL-induced root sensitivity to gravity. Interestingly, IAA treatment to the roots of bri1-301 and bak1 plants or of plants pretreated with a BL biosynthetic inhibitor, brassinazole, increased their sensitivity to gravity, while these treatments for the BL-hypersensitive transgenic plants, BRI1-GFP and 35S-BAK1, were less effective. Expression of a CYP79B2 gene, encoding an IAA biosynthetic enzyme, was suppressed in BL-hypersensitive plant types and enhanced in BL-insensitive or -deficient plants. In conclusion, our results indicate that BL interacts negatively with IAA in the regulation of plant gravitropic response and root growth, and its regulation is achieved partly by modulating biosynthetic pathways of the counterpart hormone. PMID:17470144

Kim, Tae-Wuk; Lee, Sun Min; Joo, Se-Hwan; Yun, Hye Sup; Lee, Yew; Kaufman, Peter B; Kirakosyan, Ara; Kim, Soo-Hwan; Nam, Kyoung Hee; Lee, June Seung; Chang, Soo Chul; Kim, Seong-Ki

2007-06-01

37

Derivation of formulas for root-mean-square errors in location, orientation, and shape in triangulation solution of an elongated object in space  

NASA Technical Reports Server (NTRS)

Formulas are derived for the root-mean-square (rms) displacement, slope, and curvature errors in an azimuth-elevation image trace of an elongated object in space, as functions of the number and spacing of the input data points and the rms elevation error in the individual input data points from a single observation station. Also, formulas are derived for the total rms displacement, slope, and curvature error vectors in the triangulation solution of an elongated object in space due to the rms displacement, slope, and curvature errors, respectively, in the azimuth-elevation image traces from different observation stations. The total rms displacement, slope, and curvature error vectors provide useful measure numbers for determining the relative merits of two or more different triangulation procedures applicable to elongated objects in space.

Long, S. A. T.

1974-01-01

38

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

39

A root-specific condensing enzyme from Lesquerella fendleri that elongates very-long-chain saturated fatty acids  

E-print Network

A root-specific condensing enzyme from Lesquerella fendleri that elongates very form: 12 November 2004 Key words: 3-ketoacyl-CoA synthase, fatty acid elongase, Lesquerella fendleri Lesquerella fendleri. The LfKCS45 gene has a 1464 bp open reading frame without introns, and is predicted

Kunst, Ljerka

40

Elongation of Shoot and Root in Wheat by ACC Deaminase of Rhizobium Spp. Indigenous to Soils of Iran  

Microsoft Academic Search

This study was conducted to investigate the role of 1-aminocyclopropane-1-carboxylate (ACC) deaminase in Rhizobium strains indigenous to Iranian soils and their ability to reduce stress ethylene and promote the elongation of the roots of wheat seedlings. One hundred different rhizobial strains isolated from some Iranian soils were cultured on Rhizobial Minimal Medium (RMM) with two different sources of nitrogen (ACC

ATEFEH RAMEZANIAN BAJGIRAN; AMIR LAKZIAN; NAHID SALEH-RASTIN

41

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

42

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

PubMed

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

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

2014-05-01

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

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

Liu, Ying; Lai, Ningwei; Gao, Kun; Chen, Fanjun; Yuan, Lixing; Mi, Guohua

2013-01-01

44

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. PMID:23577185

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

2013-01-01

45

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

PubMed Central

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

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

2010-01-01

46

Bacterial biosynthesis of 1-aminocyclopropane-1-caboxylate (ACC) deaminase, a useful trait to elongation and endophytic colonization of the roots of rice under constant flooded conditions.  

PubMed

This study was conducted to investigate the role of 1-aminocyclopropane-1-carboxylate (ACC) deaminase in Pseudomonas fluorescens strain REN1 and its ability to reduce ethylene levels produced during stress, endophytically colonize and promote the elongation of the roots of rice seedlings under gnotobiotic conditions. We isolated 80 bacteria from inside roots of rice plants grown in the farmers' fields in Guilan, Iran. All of the isolates were characterized for plant growth promoting (PGP) traits. In addition, the colonization assay of these isolates on rice seedlings was carried out to screen for competent endophytes. The best bacterial isolate, based on ACC deaminase production, was identified and used for further study. 16S rDNA sequence analysis revealed that the endophyte was closely related to Pseudomonas fluorescens. The results of this study showed ACC deaminase containing P. fluorescens REN1 increased in vitro root elongation and endophytically colonized the root of rice seedlings significantly, as compared to control under constant flooded conditions. The trait of low amount of indole-3-acetic acid (IAA) production (<15 ?g mL(-1)) and the high production of ACC deaminase by bacteria may be main factors in colonizing rice seedling roots compared to other PGP traits (siderophore production and phosphate solubilization) in this study. Endophytic IAA and ACC deaminase-producing bacteria may be preferential selections by rice seedlings. Therefore, it may be suggested that the utilization of ACC as a nutrient gives the isolates advantages in more endophytic colonization and increase of root length of rice seedlings. PMID:25320466

Etesami, Hassan; Mirseyed Hosseini, Hossein; Alikhani, Hossein Ali

2014-10-01

47

Selenium Inhibits Root Elongation by Repressing the Generation of Endogenous Hydrogen Sulfide in Brassica rapa  

PubMed Central

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

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

2014-01-01

48

Selenium Inhibits Root Elongation by Repressing the Generation of Endogenous Hydrogen Sulfide in Brassica rapa.  

PubMed

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

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

2014-01-01

49

Changes in intracellular and apoplastic peroxidase activity, ascorbate redox status, and root elongation induced by enhanced ascorbate content in Allium cepa L  

Microsoft Academic Search

Onions (Allium cepa L.) treated with external ascorbic acid or with the immediate precursor of its synthesis L-galactono-c-lactone show a stimulated elongation rate of the roots and an increase in the number of new radicles appearing at the bulb base. Treatment with both molecules resulted in an enhanced accumu- lation of ascorbate and dehydroascorbate along the root axis, but the

Maria del Carmen Cordoba-Pedregosa; JoseManuel Villalba; Francisco Cordoba; JoseAntonio Gonzalez-Reyes

2005-01-01

50

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. PMID:9536058

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

1998-01-01

51

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

PubMed

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

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

2014-03-01

52

The relative significance for stem elongation and flowering in Lolium temulentum of 3?-hydroxylation of gibberellins  

Microsoft Academic Search

In previous experiments with many gibberellins (GAs) and GA derivatives applied to Lolium temulentum L., quite different structural requirements were evident for stem elongation on the one hand and for the promotion of flowering on the other. Whereas hydroxylation at carbons 12, 13 and 15 enhanced flowering relative to stem growth, the reverse was the case at carbon 3 (L.T.

L. T. Evans; R. W. King; L. N. Mander; R. P. Pharis

1993-01-01

53

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

54

Humic Acids Isolated from Earthworm Compost Enhance Root Elongation, Lateral Root Emergence, and Plasma Membrane H+-ATPase Activity in Maize Roots1  

PubMed Central

Earthworms (Eisenia foetida) produce humic substances that can influence plant growth by mechanisms that are not yet clear. In this work, we investigated the effects of humic acids (HAs) isolated from cattle manure earthworm compost on the earliest stages of lateral root development and on the plasma membrane H+-ATPase activity. These HAs enhance the root growth of maize (Zea mays) seedlings in conjunction with a marked proliferation of sites of lateral root emergence. They also stimulate the plasma membrane H+-ATPase activity, apparently associated with an ability to promote expression of this enzyme. In addition, structural analysis reveals the presence of exchangeable auxin groups in the macrostructure of the earthworm compost HA. These results may shed light on the hormonal activity that has been postulated for these humic substances. PMID:12481077

Canellas, Luciano Pasqualoto; Olivares, Fabio Lopes; Okorokova-Façanha, Anna L.; Façanha, Arnoldo Rocha

2002-01-01

55

STUNTED PLANT 1, A Gene Required for Expansion in Rapidly Elongating but Not in Dividing Cells and Mediating Root Growth Responses to Applied Cytokinin.  

PubMed Central

To understand the control of spatial patterns of expansion, we have studied root growth in wild type and in the stunted plant 1 mutant, stp1, of Arabidopsis thaliana. We measured profiles of cell length and calculated the distribution of elongation rate. Slow growth of stp1 results both from a failure of dividing cell number to increase and from low elongation rates in the zone of rapid expansion. However, elongation of dividing cells was not greatly affected, and stp1 and wild-type callus grew at identical rates. Thus, rapid cellular expansion differs in mechanism from expansion in dividing cells and is facilitated by the STP1 gene. Additionally, there was no difference between stp1 and wild-type roots for elongation in response to abscisic acid, auxin, ethylene, or gibberellic acid or for radial expansion in response to ethylene; however, stp1 responded to cytokinin much less than wild type. In contrast, both genotypes responded comparably to hormones when explants were cultured; in particular, there was no difference between genotypes in shoot regeneration in response to cytokinin. Thus, effects on root expansion mediated by cytokinin, but not effects mediated by other hormones or effects on other cytokinin-mediated responses, require the STP1 locus. PMID:12228357

Baskin, T. I.; Cork, A.; Williamson, R. E.; Gorst, J. R.

1995-01-01

56

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

PubMed

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

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

2013-12-01

57

OsARF12, a transcription activator on auxin response gene, regulates root elongation and affects iron accumulation in rice (Oryza sativa).  

PubMed

• Auxin has an important role in maintaining optimal root system architecture (RSA) that can cope with growth reductions of crops caused by water or nutrient shortages. However, the mechanism of controlling RSA remains largely unclear. Here, we found a limiting factor of RSA--OsARF12--an auxin response factor whose knockout led to decreased primary root length in rice (Oryza sativa). • OsARF12 as a transcription activator can facilitate the expression of the auxin response element DR5::GFP, and OsARF12 was inhibited by osa-miRNA167d by transient expression in tobacco and rice callus. • The root elongation zones of osarf12 and osarf12/25, which had lower auxin concentrations, were distinctly shorter than for the wild-type, possibly as a result of decreased expression of auxin synthesis genes OsYUCCAs and auxin efflux carriers OsPINs and OsPGPs. The knockout of OsARF12 also altered the abundance of mitochondrial iron-regulated (OsMIR), iron (Fe)-regulated transporter1 (OsIRT1) and short postembryonic root1 (OsSPR1) in roots of rice, and resulted in lower Fe content. • The data provide evidence for the biological function of OsARF12, which is implicated in regulating root elongation. Our investigation contributes a novel insight for uncovering regulation of RSA and the relationship between auxin response and Fe acquisition. PMID:21973088

Qi, YanHua; Wang, SuiKang; Shen, ChenJia; Zhang, SaiNa; Chen, Yue; Xu, YanXia; Liu, Yu; Wu, YunRong; Jiang, DeAn

2012-01-01

58

Rooting depths of plants relative to biological and environmental factors  

SciTech Connect

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

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

1984-11-01

59

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

Microsoft Academic Search

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

S. N. Shabala; I. A. Newman

1998-01-01

60

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

E-print Network

CHEMICAL ROOT PRUNING AND ITS EFFECTS ON WATER RELATIONS AND ROOT MORPHOLOGY OF PHOT1IVIA A Thesis by DIPTISH RAMESH VARTAK Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1993 Major Subject: Agricultural Engineering CHEMICAL ROOT PRUNING AND ITS EFFECTS ON WATER RELATIONS AND ROOT MORPHOLOGY OF PHOTJIVIA A Thesis by DIPTISH RAMESH VARTAK Submitted to Texas A&M University...

Vartak, Diptish Ramesh

2012-06-07

61

A root-specific condensing enzyme from Lesquerella fendleri that elongates very-long-chain saturated fatty acids.  

PubMed

The LfKCS45 gene with a high sequence similarity to known 3-ketoacyl-CoA synthases of the membrane-bound fatty acid elongase was isolated from Lesquerella fendleri. The LfKCS45 gene has a 1464 bp open reading frame without introns, and is predicted to encode a polypeptide of 487 amino acids with an estimated molecular mass of 54.6 kD. High-stringency DNA blot analysis indicated that there were no closely related genes to LfKCS45 in the L. fendleri genome. Analysis of the fatty acid composition of transformed yeast revealed that expression of the LfKCS45 protein results in the synthesis of two novel very-long-chain fatty acids identified as C28:0 and C30:0. LfKCS45 was found to be not active with acyl-CoA substrates C16 to C24 in length. Reverse transcription-PCR experiments showed that the LfKCS45 gene is expressed only in L. fendleri root tips. Histochemical assays for GUS activity in Arabidopsis transformed with the LfKCS45 promoter-GUS fusion construct confirmed this expression pattern and demonstrated that LfKCS45 transcription is restricted to the cells of the lateral root cap. PMID:15821990

Moon, Hangsik; Chowrira, Gangamma; Rowland, Owen; Blacklock, Brenda J; Smith, Mark A; Kunst, Ljerka

2004-12-01

62

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. PMID:8636234

1996-01-01

63

Turbulent Drag Reduction of polyelectrolyte (DNA) solutions relation with the elongational viscosity  

E-print Network

We report measurements of turbulent drag reduction of two different polyelectrolyte solutions: DNA and hydrolyzed Polyacrylamide. Changing the salt concentration in the solutions allows us to change the flexibility of the polymer chains. For both polymers the amount of drag reduction was found to increase with the flexibility. Rheological studies reveal that the elongational viscosity of the solutions increases simultaneously. Hence we conclude that the elongational viscosity is the pertinent macroscopic quantity to describe the ability of a polymer to cause turbulent drag reduction.

Wagner, C; Doyle, P G; Bonn, D A; Wagner, Christian; Amarouchene, Yassine; Doyle, Patrick; Bonn, Daniel

2001-01-01

64

Proline Accumulation in Maize (Zea mays L.) Primary Roots at Low Water Potentials. II. Metabolic Source of Increased Proline Deposition in the Elongation Zone1  

PubMed Central

The proline (Pro) concentration increases greatly in the growing region of maize (Zea mays L.) primary roots at low water potentials (?w), largely as a result of an increased net rate of Pro deposition. Labeled glutamate (Glu), ornithine (Orn), or Pro was supplied specifically to the root tip of intact seedlings in solution culture at high and low ?w to assess the relative importance of Pro synthesis, catabolism, utilization, and transport in root-tip Pro deposition. Labeling with [3H]Glu indicated that Pro synthesis from Glu did not increase substantially at low ?w and accounted for only a small fraction of the Pro deposition. Labeling with [14C]Orn showed that Pro synthesis from Orn also could not be a substantial contributor to Pro deposition. Labeling with [3H]Pro indicated that neither Pro catabolism nor utilization in the root tip was decreased at low ?w. Pro catabolism occurred at least as rapidly as Pro synthesis from Glu. There was, however, an increase in Pro uptake at low ?w, which suggests increased Pro transport. Taken together, the data indicate that increased transport of Pro to the root tip serves as the source of low-?w-induced Pro accumulation. The possible significance of Pro catabolism in sustaining root growth at low ?w is also discussed. PMID:10198094

Verslues, Paul E.; Sharp, Robert E.

1999-01-01

65

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

PubMed Central

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

Durr, Julius; Lolas, Ihab B.; S?rensen, Brian B.; Schubert, Veit; Houben, Andreas; Melzer, Michael; Deutzmann, Rainer; Grasser, Marion; Grasser, Klaus D.

2014-01-01

66

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

67

Ubiquitin-Related Modifiers of Arabidopsis thaliana Influence Root Development  

PubMed Central

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

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

2014-01-01

68

Inhibition of Al-induced root elongation and enhancement of Al-induced peroxidase activity in Al-sensitive and Al-resistant barley cultivars are positively correlated  

Microsoft Academic Search

The quantitative changes in peroxidase activity and composition of anionic and cationic isoperoxidases were investigated in roots of two barley cultivars differing in Al resistance. Root growth of Al-resistant cv. Bavaria was in lesser extent reduced by Al treatment (23% after 24 h Al-treatment), whereas 40% reduction of the root growth was observed in Al-sensitive cv. Alfor. The strong root

Ladislav Tamás; Jana Huttová; Igor Mistrík

2003-01-01

69

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

70

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

2011-08-01

71

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

PubMed Central

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

Marzec, Marek

2013-01-01

72

Quantum root-mean-square error and measurement uncertainty relations  

E-print Network

Recent years have witnessed a controversy over Heisenberg's famous error-disturbance relation. Here we resolve the conflict by way of an analysis of the possible conceptualizations of measurement error and disturbance in quantum mechanics. We discuss two approaches to adapting the classic notion of root-mean-square error to quantum measurements. One is based on the concept of noise operator; its natural operational content is that of a mean deviation of the values of two observables measured jointly, and thus its applicability is limited to cases where such joint measurements are available. The second error measure quantifies the differences between two probability distributions obtained in separate runs of measurements and is of unrestricted applicability. We show that there are no nontrivial unconditional joint-measurement bounds for {\\em state-dependent} errors in the conceptual framework discussed here, while Heisenberg-type measurement uncertainty relations for {\\em state-independent} errors have been proven.

Paul Busch; Pekka Lahti; Reinhard F Werner

2013-12-16

73

Inactivation of Plasma Membrane-Localized CDPK-RELATED KINASE5 Decelerates PIN2 Exocytosis and Root Gravitropic Response in Arabidopsis[C][W  

PubMed Central

CRK5 is a member of the Arabidopsis thaliana Ca2+/calmodulin-dependent kinase-related kinase family. Here, we show that inactivation of CRK5 inhibits primary root elongation and delays gravitropic bending of shoots and roots. Reduced activity of the auxin-induced DR5–green fluorescent protein reporter suggests that auxin is depleted from crk5 root tips. However, no tip collapse is observed and the transcription of genes for auxin biosynthesis, AUXIN TRANSPORTER/AUXIN TRANSPORTER-LIKE PROTEIN (AUX/LAX) auxin influx, and PIN-FORMED (PIN) efflux carriers is unaffected by the crk5 mutation. Whereas AUX1, PIN1, PIN3, PIN4, and PIN7 display normal localization, PIN2 is depleted from apical membranes of epidermal cells and shows basal to apical relocalization in the cortex of the crk5 root transition zone. This, together with an increase in the number of crk5 lateral root primordia, suggests facilitated auxin efflux through the cortex toward the elongation zone. CRK5 is a plasma membrane–associated kinase that forms U-shaped patterns facing outer lateral walls of epidermis and cortex cells. Brefeldin inhibition of exocytosis stimulates CRK5 internalization into brefeldin bodies. CRK5 phosphorylates the hydrophilic loop of PIN2 in vitro, and PIN2 shows accelerated accumulation in brefeldin bodies in the crk5 mutant. Delayed gravitropic response of the crk5 mutant thus likely reflects defective phosphorylation of PIN2 and deceleration of its brefeldin-sensitive membrane recycling. PMID:23673979

Rigo, Gabor; Ayaydin, Ferhan; Tietz, Olaf; Zsigmond, Laura; Kovacs, Hajnalka; Pay, Aniko; Salchert, Klaus; Darula, Zsuzsanna; Medzihradszky, Katalin F.; Szabados, Laszlo; Palme, Klaus; Koncz, Csaba; Cseplo, Agnes

2013-01-01

74

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

PubMed

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

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

2013-05-01

75

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. PMID:20639301

Useche, Antonio; Shipley, Bill

2010-01-01

76

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

EPA Science Inventory

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

77

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

PubMed

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

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

2014-10-01

78

Carbon unloading in roots in relation to root senescence in Cercis chinensis seedlings under drought stress  

Microsoft Academic Search

When Cercis chinensis seedlings suffered from drought treatment, net photosynthetic rates had been significantly reduced at the end of the drought\\u000a treatment. Compared with the control, the activities of acid invertases in roots had increased 5 and 11 days after drought\\u000a treatment. Seventeen days after drought treatment, the activities of acid invertases in roots were significantly decreased,\\u000a while activities of

Cai-xia Gan; Chu Wu

2009-01-01

79

Influence of gibberellin biosynthesis inhibitors on stem elongation and floral initiation on in vitro chicory root explants under dark and light conditions  

Microsoft Academic Search

Root explants of chicory (Cichorium intybus L.) were cultured in vitro under continuous light or darkness. On a standard medium (no plant growth regulators added), flowering-stems were initiated under continuous light while under continuous dark, vegetative-stems were formed. Different types of GA (gibberellin) biosynthesis inhibitors were added to the culture medium. Paclobutrazol and compounds belonging to the group of cyclohexanetriones

M. A. C. Demeulemeester; W. Rademacher; A. Mierop; M. P. Proft

1995-01-01

80

Control of Transcriptional Elongation  

PubMed Central

Elongation is becoming increasingly recognized as a critically controlled step in transcriptional regulation. While traditional genetic and biochemical studies have identified major players of transcriptional elongation, our understanding of the importance and roles of these factors is evolving rapidly through the recent advances in genome-wide and single-molecule technologies. Here we focus on how elongation can modulate the transcriptional outcome through the rate-liming step of RNA polymerase II pausing near promoters, and how the participating factors were identified. Among the factors we describe are NELF and DSIF, the pausing factors, and P-TEFb, the key player in pause release. We also describe non-exclusive models for how pausing is achieved by making use of high resolution genome-wide mapping of paused Pol II relative to promoter elements and the first nucleosome. We also discuss Pol II elongation through the bodies of genes and the roles of FACT and Spt6, the factors that allow Pol II to move through nucleosomes. PMID:24050178

Kwak, Hojoong; Lis, John T.

2014-01-01

81

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

82

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

83

Biosensor reporting of root exudation from Hordeum vulgare in relation to shoot nitrate concentration.  

PubMed

The aim of this study was to determine the relationship between shoot nitrate concentration, mediated by nitrate supply to roots, and root exudation from Hordeum vulgare. Plants were grown for 14 d in C-free sand microcosms, supplied with nutrient solution containing 2 mM nitrate. After this period, three treatments were applied for a further 14 d: (A) continued supply with 2 mM nitrate (zero boost), (B) supply with 10 mM nitrate (low boost), and (C) supply with 20 mM nitrate (high boost). At the end of the treatment period, a bacterial biosensor (Pseudomonas fluorescens 10586 pUCD607, marked with the lux CDABE genes for bioluminescence) was applied to the microcosms to report on C-substrate availability, as a consequence of root exudation. The nitrate boost treatments significantly affected shoot nitrate concentrations, in the order C>B>A. In treatments receiving a nitrate boost (B, C), increased shoot nitrate concentration was correlated with increased plant biomass, reduced root length, reduced number of root tips, and increased mean root diameter, relative to the no boost treatment (A). Imaging of biosensor bioluminescence (proportional to metabolic activity in response to availability of root exudates) indicated that root exudation increased with decreasing shoot nitrate concentration. Biosensor reporting of root C-flow indicated that exudation was greater from root tip regions than from the whole root, but that specific exudation rates for all sites were unaffected by treatments. Total root exudation across treatments was found to be closely correlated with total root length, indicating that increased root exudation, per unit root biomass, with decreasing nitrate supply was associated with altered root morphology, as a consequence of systemic plant responses to internal N-status. PMID:12493860

Darwent, Marcus J; Paterson, Eric; McDonald, A James S; Tomos, A Deri

2003-01-01

84

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

PubMed Central

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, Desiree; Monshausen, Gabriele B.; Dubrovsky, Joseph G.; Bednarova, Andrea; Krishnan, Natraj

2013-01-01

85

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

PubMed Central

The rhizotoxicities of Al3+ and of La3+ to wheat (Triticum aestivum L.) were similarly ameliorated by cations in the following order of effectiveness: H+ ? C3+ > C2+ > C1+. Among tested cations of a given charge, ameliorative effectiveness was similar except that Ca2+ was slightly more effective than other divalent cations and H+ was much more effective than other monovalent cations. H+ rhizotoxicity was also ameliorated by cations in the order C3+ > C2+ > C1+. These results suggest a role for cell-surface electrical potential in the rhizotoxicity of Al3+, La3+, H+, and other toxic cations: negatively charged cell surfaces of the root accumulate the toxic cations, and amelioration is effected by treatments that reduce the negativity of the cell-surface electrical potential by charge screening or cation binding. Membrane-surface activities of free Al3+ or La3+ computed according to a Gouy-Chapman-Stern model correlated well with growth inhibition, which correlated only poorly with Al3+ or La3+ activities in the external medium. The similar responses of Al-intoxicated and La-intoxicated roots to ameliorative treatments provide evidence that Al3+, rather than AlOH2+ or Al(OH)2+, is the principal toxic species of mononuclear Al. Comparisons of the responses of Al-sensitive and Al-tolerant wheats to Al3+ and to La3+ did not support the hypothesis that varietal sensitivity to Al3+ is based upon differences in cell-surface electrical potential. PMID:16669059

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

1992-01-01

86

Functional implications related to the gene structure of the elongation factor EF-Tu from Halobacterium marismortui.  

PubMed

The primary structure of the gene for the elongation factor EF-Tu from the halophilic archaebacterium Halobacterium marismortui (hEF-Tu) is described. It is the first gene of a halophilic elongation factor EF-Tu to be sequenced. When the sequence of hEF-Tu is compared to that of homologous proteins from other organisms, the highest identity (61%) is found with EF-Tu from Methanococcus vannielii, a non-halophilic archaebacterium. In the search for halophilic characteristics therefore the most appropriate comparison is with the M. vannielii sequence. The excess of acidic amino acid residues in the hEF-Tu sequence (already observed in the composition of other halophilic proteins) results to a large extent from changes of Lys, Asn or Gln to Asp or Glu. A structural analysis algorithm applied to the halophilic sequence places these acidic residues on the surface of the protein. The corresponding residues in the crystal structure of the first domain of EF-Tu from E. coli (the only EF-Tu structure available) are grouped in patches on the protein surface, in each of which several residues that may be far apart in the sequence come quite close to each other in the tertiary structure. PMID:2155402

Baldacci, G; Guinet, F; Tillit, J; Zaccai, G; de Recondo, A M

1990-02-11

87

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

PubMed Central

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

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

2009-01-01

88

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

PubMed

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

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

2013-09-01

89

Aconitum Alkaloid Poisoning Related to the Culinary Uses of Aconite Roots  

PubMed Central

Aconite roots (roots or root tubers of the Aconitum species) are eaten as root vegetables and used to prepare herbal soups and meals, mainly for their purported health benefits. Aconite roots contain aconitine and other Aconitum alkaloids, which are well known cardiotoxins and neurotoxins. To better understand why Aconitum alkaloid poisoning related to the culinary uses of aconite roots can occur and characterize the risks posed by these “food supplements”, relevant published reports were reviewed. From 1995 to 2013, there were eight reports of aconite poisoning after consumption of these herbal soups and meals, including two reports of large clusters of cases (n = 19–45) and two reports of cases (n = 15–156) managed by two hospitals over a period of 4.5 to 5 years. The herbal formulae used did not adhere to the suggested guidelines, with regarding to the doses (50–500 g instead of 3–30 g per person) and types (raw instead of processed) of aconite roots used. The quantities of Aconitum alkaloids involved were huge, taking into consideration the doses of aconite roots used to prepare herbal soups/meals and the amounts of aconite roots and herbal soups/meals consumed. In a large cluster of cases, despite simmering raw “caowu” (the root tuber of A. kusnezoffii) in pork broth for 24 h, all 19 family members who consumed this soup and boiled “caowu” developed poisoning. Severe or even fatal aconite poisoning can occur after consumption of herbal soups and foods prepared from aconite roots. Even prolonged boiling may not be protective if raw preparations and large quantities of aconite roots are used. The public should be warned of the risk of severe poisoning related to the culinary and traditional medicinal uses of aconite roots. PMID:25184557

Chan, Thomas Y. K.

2014-01-01

90

Aconitum alkaloid poisoning related to the culinary uses of aconite roots.  

PubMed

Aconite roots (roots or root tubers of the Aconitum species) are eaten as root vegetables and used to prepare herbal soups and meals, mainly for their purported health benefits. Aconite roots contain aconitine and other Aconitum alkaloids, which are well known cardiotoxins and neurotoxins. To better understand why Aconitum alkaloid poisoning related to the culinary uses of aconite roots can occur and characterize the risks posed by these "food supplements", relevant published reports were reviewed. From 1995 to 2013, there were eight reports of aconite poisoning after consumption of these herbal soups and meals, including two reports of large clusters of cases (n = 19-45) and two reports of cases (n = 15-156) managed by two hospitals over a period of 4.5 to 5 years. The herbal formulae used did not adhere to the suggested guidelines, with regarding to the doses (50-500 g instead of 3-30 g per person) and types (raw instead of processed) of aconite roots used. The quantities of Aconitum alkaloids involved were huge, taking into consideration the doses of aconite roots used to prepare herbal soups/meals and the amounts of aconite roots and herbal soups/meals consumed. In a large cluster of cases, despite simmering raw "caowu" (the root tuber of A. kusnezoffii) in pork broth for 24 h, all 19 family members who consumed this soup and boiled "caowu" developed poisoning. Severe or even fatal aconite poisoning can occur after consumption of herbal soups and foods prepared from aconite roots. Even prolonged boiling may not be protective if raw preparations and large quantities of aconite roots are used. The public should be warned of the risk of severe poisoning related to the culinary and traditional medicinal uses of aconite roots. PMID:25184557

Chan, Thomas Y K

2014-09-01

91

The ASH1-RELATED3 SET-Domain Protein Controls Cell Division Competence of the Meristem and the Quiescent Center of the Arabidopsis Primary Root.  

PubMed

The stem cell niche of the Arabidopsis (Arabidopsis thaliana) primary root apical meristem is composed of the quiescent (or organizing) center surrounded by stem (initial) cells for the different tissues. Initial cells generate a population of transit-amplifying cells that undergo a limited number of cell divisions before elongating and differentiating. It is unclear whether these divisions occur stochastically or in an orderly manner. Using the thymidine analog 5-ethynyl-2'-deoxyuridine to monitor DNA replication of cells of Arabidopsis root meristems, we identified a pattern of two, four, and eight neighboring cells with synchronized replication along the cortical, epidermal, and endodermal cell files, suggested to be daughters, granddaughters, and great-granddaughters of the direct progeny of each stem cell. Markers of mitosis and cytokinesis were not present in the region closest to the transition zone where the cells start to elongate, suggesting that great-granddaughter cells switch synchronously from the mitotic cell cycle to endoreduplication. Mutations in the stem cell niche-expressed ASH1-RELATED3 (ASHR3) gene, encoding a SET-domain protein conferring histone H3 lysine-36 methylation, disrupted this pattern of coordinated DNA replication and cell division and increased the cell division rate in the quiescent center. E2Fa/E2Fb transcription factors controlling the G1-to-S-phase transition regulate ASHR3 expression and bind to the ASHR3 promoter, substantiating a role for ASHR3 in cell division control. The reduced length of the root apical meristem and primary root of the mutant ashr3-1 indicate that synchronization of replication and cell divisions is required for normal root growth and development. PMID:25034019

Kumpf, Robert; Thorstensen, Tage; Rahman, Mohummad Aminur; Heyman, Jefri; Nenseth, H Zeynep; Lammens, Tim; Herrmann, Ullrich; Swarup, Ranjan; Veiseth, Silje Veie; Emberland, Gitika; Bennett, Malcolm J; De Veylder, Lieven; Aalen, Reidunn B

2014-10-01

92

Relative importance of an arbuscular mycorrhizal fungus (Rhizophagus intraradices) and root hairs in plant drought tolerance.  

PubMed

Both arbuscular mycorrhizal (AM) fungi and root hairs play important roles in plant uptake of water and mineral nutrients. To reveal the relative importance of mycorrhiza and root hairs in plant water relations, a bald root barley (brb) mutant and its wild type (wt) were grown with or without inoculation of the AM fungus Rhizophagus intraradices under well-watered or drought conditions, and plant physiological traits relevant to drought stress resistance were recorded. The experimental results indicated that the AM fungus could almost compensate for the absence of root hairs under drought-stressed conditions. Moreover, phosphorus (P) concentration, leaf water potential, photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency were significantly increased by R. intraradices but not by root hairs, except for shoot P concentration and photosynthetic rate under the drought condition. Root hairs even significantly decreased root P concentration under drought stresses. These results confirm that AM fungi can enhance plant drought tolerance by improvement of P uptake and plant water relations, which subsequently promote plant photosynthetic performance and growth, while root hairs presumably contribute to the improvement of plant growth and photosynthetic capacity through an increase in shoot P concentration. PMID:24743902

Li, Tao; Lin, Ge; Zhang, Xin; Chen, Yongliang; Zhang, Shubin; Chen, Baodong

2014-11-01

93

The Elongation of Ovococci  

PubMed Central

The morphogenesis of ovococci has been reviewed extensively. Recent results have provided new insights concerning the mechanisms of elongation in ovoid bacteria. We present here the proteins involved in the elongation (firmly established and more or less hypothetical) and discuss the relationship between elongation and division of ovococci. PMID:24773288

Philippe, Jules; Vernet, Thierry

2014-01-01

94

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. PMID:20682788

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

95

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

PubMed

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

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

2014-01-01

96

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

PubMed Central

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

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

2014-01-01

97

Root hairs.  

PubMed

Roots hairs are cylindrical extensions of root epidermal cells that are important for acquisition of nutrients, microbe interactions, and plant anchorage. The molecular mechanisms involved in the specification, differentiation, and physiology of root hairs in Arabidopsis are reviewed here. Root hair specification in Arabidopsis is determined by position-dependent signaling and molecular feedback loops causing differential accumulation of a WD-bHLH-Myb transcriptional complex. The initiation of root hairs is dependent on the RHD6 bHLH gene family and auxin to define the site of outgrowth. Root hair elongation relies on polarized cell expansion at the growing tip, which involves multiple integrated processes including cell secretion, endomembrane trafficking, cytoskeletal organization, and cell wall modifications. The study of root hair biology in Arabidopsis has provided a model cell type for insights into many aspects of plant development and cell biology. PMID:24982600

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

2014-01-01

98

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 PMID:3782459

Haapasalo, M

1986-01-01

99

Elongational rheology of polyethylene melts  

NASA Astrophysics Data System (ADS)

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

Seyfzadeh, Bijan

100

Relation of the Occurrence of Cotton Root Rot to the Chemical Composition of Soils.  

E-print Network

:~p$ne$$ 9 -FK~( Q9"y.a *e4*&; I * Relation of the occurrence of Cotton Root7*'. Rot to the Chemical Composition of Soils -- AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS T. 0. WALTON, President Soils in which cotton root rot generally occurs... does not generally occur on these soils. This indicates the action of inhibitory factors in alluvial soils not usually operative to the same degree in heavy upland soils. The chemical colnposition of local areas of soil containing active root rot...

Fraps, G. S. (George Stronach); Fudge, J. F. (Joseph Franklin)

1935-01-01

101

Kazan and Manchu: Cultural Roots of Soviet Foreign Relations  

Microsoft Academic Search

Proceeding from the assumption that there is a living past influencing decision-makers' images of their country and the world, this article discusses probable conscious and subconscious perceptions of the nature of Russia's foreign relations among the present Soviet leadership. The article argues that Soviet leaders have been used to looking upon the foreign relations of their state as one of

Kristian Gerner

1980-01-01

102

Sugar beet root shape and its relation with yield and quality  

Microsoft Academic Search

In a two-year (2002–2003) field study, six sugar beet cultivars were arranged in a Randomised Complete Block design with six\\u000a replications. The aim of the work was to study the root shape variability using an image analysis system and to relate root\\u000a shape parameters [area (A, cm2), maximum length (L, cm), maximum width (W, cm), average radial (AR, cm), radial

J. T. Tsialtas; N. Maslaris

2010-01-01

103

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

PubMed Central

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

2014-01-01

104

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

105

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

Microsoft Academic Search

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

Louise St-Cyr; Peter G. C. Campbell

1996-01-01

106

Complex physiological and molecular processes underlying root gravitropism  

NASA Technical Reports Server (NTRS)

Gravitropism allows plant organs to guide their growth in relation to the gravity vector. For most roots, this response to gravity allows downward growth into soil where water and nutrients are available for plant growth and development. The primary site for gravity sensing in roots includes the root cap and appears to involve the sedimentation of amyloplasts within the columella cells. This process triggers a signal transduction pathway that promotes both an acidification of the wall around the columella cells, an alkalinization of the columella cytoplasm, and the development of a lateral polarity across the root cap that allows for the establishment of a lateral auxin gradient. This gradient is then transmitted to the elongation zones where it triggers a differential cellular elongation on opposite flanks of the central elongation zone, responsible for part of the gravitropic curvature. Recent findings also suggest the involvement of a secondary site/mechanism of gravity sensing for gravitropism in roots, and the possibility that the early phases of graviresponse, which involve differential elongation on opposite flanks of the distal elongation zone, might be independent of this auxin gradient. This review discusses our current understanding of the molecular and physiological mechanisms underlying these various phases of the gravitropic response in roots.

Chen, Rujin; Guan, Changhui; Boonsirichai, Kanokporn; Masson, Patrick H.

2002-01-01

107

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

PubMed Central

Roots of white spruce seedlings (Picea glauca [Moench] Voss) undergo respiratory changes during the year that are related to changing metabolic requirements. An alternative pathway is always present, functions during most of the year, and operates maximally during periods of root and shoot growth. Although some differences in respiration and the apportioning of respiration can be correlated to root morphology, the environment and the stage of shoot development are also important controls. Differences in respiration related to root morphology are not manifest in mitochondrial structure, but overall rates were found to correlate with the number of mitochondria present. Root respiration in seedlings grown under root growth capacity conditions reflects root and shoot growth at that time rather than root growth capacity. PMID:16664776

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

1986-01-01

108

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

109

Homology of the internal sac components in the leaf beetle subfamily Criocerinae and evolutionary novelties related to the extremely elongated flagellum.  

PubMed

Extremely elongated intromittent organs are found in a wide range of taxa, especially among insects. This phenomenon is generally thought to result from sexual selection, but it is predicted that limited storage space in the body cavity and the difficulty of using the elongated organs should have constrained the evolution of extreme elongation, neutralizing any selective advantage. Therefore, in groups with long intromittent organs, features that overcome these constraints may have evolved or coevolved together with intromittent organ elongation. Using a comparative morphological approach and outgroup comparisons, we identified potential constraints and key novelties that may neutralize such constraints in the leaf beetle subfamily Criocerinae. Observations of the internal sac structure throughout Criocerinae were performed. Comparing the results with preceding studies from outgroups, a ground plan of the criocerine internal sac was constructed. Our analysis also identified specific features that are always correlated with extreme elongation: the rotation of whole internal-sac sclerites and the possession of a pocket in which to store the elongated flagellum. The pocket is thought to be formed by the rotation of the sclerites, markedly altering internal sac shape from the criocerine ground plan. Onlythe clades that have acquired this derived state contain species with an elongated flagellum that distinctly exceeds the median lobe length. It is presumed that these character correlations evolved independently three times. The detected character correlations corroborate the hypothesis that there are latent adaptive constraints for the evolution of extremely elongated intromittent organs. The constraints may have been neutralized by the alteration from the criocerine ground plan resulting in the formation of a storage pocket. In conclusion, deviation from the criocerine ground plan is considered to be the evolutionary innovation that neutralized the latent adaptive constraints of flagellum elongation in the subfamily Criocerinae. PMID:22147465

Matsumura, Yoko; Yoshizawa, Kazunori

2012-05-01

110

Computer based imaging and analysis of root gravitropism  

NASA Technical Reports Server (NTRS)

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

Evans, M. L.; Ishikawa, H.

1997-01-01

111

Computer based imaging and analysis of root gravitropism.  

PubMed

Two key issues in studies of the nature of the gravitropic response in roots have been the determination of the precise pattern of differential elongation responsible for downward bending and the identification of the cells that show the initial motor response. The main approach for examining patterns of differential growth during root gravitropic curvature has been to apply markers to the root surface and photograph the root at regular intervals during gravitropic curvature. Although these studies have provided valuable information on the characteristics of the gravitropic motor response in roots, their labor intensive nature limits sample size and discourages both high frequency of sampling and depth of analysis of surface expansion data. In this brief review we describe the development of computer-based video analysis systems for automated measurement of root growth and shape change and discuss some key features of the root gravitropic response that have been revealed using this methodology. We summarize the capabilities of several new pieces of software designed to measure growth and shape changes in graviresponding roots and describe recent progress in developing analysis systems for studying the small, but experimentally popular, primary roots of Arabidopsis. A key finding revealed by such studies is that the initial gravitropic response of roots of maize and Arabidopsis occurs in the distal elongation zone (DEZ) near the root apical meristem, not in the main elongation zone. Another finding is that the initiation of rapid elongation in the DEZ following gravistimulation appears to be related to rapid membrane potential changes in this region of the root. These observations have provided the incentive for ongoing studies examining possible links between potential growth modifying factors (auxin, calcium, protons) and gravistimulated changes in membrane potential and growth patterns in the DEZ. PMID:11540122

Evans, M L; Ishikawa, H

1997-06-01

112

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

113

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

E-print Network

-1 Relative contribution of initial root and shoot morphology in predicting field performance of hardwood seedlings D.F. JACOBS1,* , K.F. SALIFU1 and J.R. SEIFERT2 1 Department of Forestry and Natural, USA; 2 Department of Forestry and Natural Resources, Southheast Purdue Agricultural Center, Purdue

114

Isolation and characterization of a short lateral root mutant in rice ( Oryza sativa L.)  

Microsoft Academic Search

Proper initiation and elongation of lateral roots are the important factors that determine the architecture of plant roots. However, little is known about the mechanisms controlling lateral root elongation. In an effort to understand the mechanisms of lateral root elongation in rice, a monogenic recessive mutant, alf1 (altered lateral root formation) has been isolated from tissue culture-derived R1 lines. The

Bakul Rani Debi; Junko Mushika; Shin Taketa; Akio Miyao; Hirohiko Hirochika; Masahiko Ichii

2003-01-01

115

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

NASA Astrophysics Data System (ADS)

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

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

116

Elongated Polyproline Motifs Facilitate Enamel Evolution through Matrix Subunit Compaction  

E-print Network

Elongated Polyproline Motifs Facilitate Enamel Evolution through Matrix Subunit Compaction Tianquan mineral component of relatively light-weight, articulated endoskeletons and sophisticated tooth, Dangaria S, Walker C, et al. (2009) Elongated Polyproline Motifs Facilitate Enamel Evolution through Matrix

Braatz, Richard D.

117

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

118

Synthesis of Elongated Microcapsules  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

119

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

PubMed

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. PMID:23002434

Xu, Weifeng; Jia, Liguo; Baluška, František; Ding, Guochang; Shi, Weiming; Ye, Nenghui; Zhang, Jianhua

2012-10-01

120

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

2013-11-15

121

Resistance in tomato and wild relatives to crown and root rot caused by Phytophthora capsici.  

PubMed

Phytophthora capsici causes root, crown, and fruit rot of tomato, a major vegetable crop grown worldwide. The objective of this study was to screen tomato cultivars and wild relatives of tomato for resistance to P. capsici. Four P. capsici isolates were individually used to inoculate 6-week-old seedlings (1 g of P. capsici-infested millet seed per 10 g of soilless medium) of 42 tomato cultivars and wild relatives of tomato in a greenhouse. Plants were evaluated daily for wilting and death. All P. capsici isolates tested caused disease in seedlings but some isolates were more pathogenic than others. A wild relative of cultivated tomato, Solanum habrochaites accession LA407, was resistant to all P. capsici isolates tested. Moderate resistance to all isolates was identified in the host genotypes Ha7998, Fla7600, Jolly Elf, and Talladega. P. capsici was frequently recovered from root and crown tissue of symptomatic inoculated seedlings but not from leaf tissue or asymptomatic or control plants. The phenotype of the recovered isolate matched the phenotype of the inoculum. Pathogen presence was confirmed in resistant and moderately resistant tomato genotypes by species-specific polymerase chain reaction of DNA from infected crown and root tissue. Amplified fragment length polymorphisms of tomato genotypes showed a lack of correlation between genetic clusters and susceptibility to P. capsici, indicating that resistance is distributed in several tomato lineages. The results of this study create a baseline for future development of tomato cultivars resistant to P. capsici. PMID:20465418

Quesada-Ocampo, L M; Hausbeck, M K

2010-06-01

122

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...

123

Age and site-related patterns of carbon allocation to wood, foliage and roots on reclaimed kaolin mines in Georgia  

SciTech Connect

We quantified merchantable stand volume, leaf area indices (LAI), and root densities in twelve Pinus taeda L. forests growing on reclaimed kaolin mines in Georgia. Stands were 11 to 36 yrs old, and formed two productivity classes, Projected wood volume on the poor sites ranged 104 to 142 m{sup 3}/ha and from 164 to 298 on the better sites. LAI was not related to age on either the good or poor sites, LAIs reach their maximal values early in stand development (<12 yrs). Fine roots (0-1 mm) within the upper 1 m were most abundant on the poorer sites. Roots were nearly absent at depths>50 cm in stands aged 14 or less, but neatly equal in density to surface roots in the older stands. Stand age was strongly and negatively related to fine root density on both site types. Densities of larger, more perennial roots (1-2 mm) decreased with stand age on poor sites and increased on good sites. Stand productivity is closely related to LAI, and root densities show that trees allocate more energy into fine, absorbing roots on the poorer sites. Deep fine root densities indicate that trees must explore progressively greater volumes of soil to meet water and nutritional needs in reclaimed soils.

Legerski, A.; Hendrick, R.; Ogden, E.

1996-12-31

124

The ASH1-RELATED3 SET-Domain Protein Controls Cell Division Competence of the Meristem and the Quiescent Center of the Arabidopsis Primary Root1[W][OPEN  

PubMed Central

The stem cell niche of the Arabidopsis (Arabidopsis thaliana) primary root apical meristem is composed of the quiescent (or organizing) center surrounded by stem (initial) cells for the different tissues. Initial cells generate a population of transit-amplifying cells that undergo a limited number of cell divisions before elongating and differentiating. It is unclear whether these divisions occur stochastically or in an orderly manner. Using the thymidine analog 5-ethynyl-2?-deoxyuridine to monitor DNA replication of cells of Arabidopsis root meristems, we identified a pattern of two, four, and eight neighboring cells with synchronized replication along the cortical, epidermal, and endodermal cell files, suggested to be daughters, granddaughters, and great-granddaughters of the direct progeny of each stem cell. Markers of mitosis and cytokinesis were not present in the region closest to the transition zone where the cells start to elongate, suggesting that great-granddaughter cells switch synchronously from the mitotic cell cycle to endoreduplication. Mutations in the stem cell niche-expressed ASH1-RELATED3 (ASHR3) gene, encoding a SET-domain protein conferring histone H3 lysine-36 methylation, disrupted this pattern of coordinated DNA replication and cell division and increased the cell division rate in the quiescent center. E2Fa/E2Fb transcription factors controlling the G1-to-S-phase transition regulate ASHR3 expression and bind to the ASHR3 promoter, substantiating a role for ASHR3 in cell division control. The reduced length of the root apical meristem and primary root of the mutant ashr3-1 indicate that synchronization of replication and cell divisions is required for normal root growth and development. PMID:25034019

Kumpf, Robert; Thorstensen, Tage; Rahman, Mohummad Aminur; Heyman, Jefri; Nenseth, H. Zeynep; Lammens, Tim; Herrmann, Ullrich; Swarup, Ranjan; Veiseth, Silje Veie; Emberland, Gitika; Bennett, Malcolm J.; De Veylder, Lieven; Aalen, Reidunn B.

2014-01-01

125

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

E-print Network

of the soil. Laboratory studies of the growth of the fungus on culture media showed that it grew best at about the neutral point, pH 7.0, and that it would not grow so well in more acid or in more alkaline media. Cotton fields in 16 counties of Texas were... examined, and the acidity or alkalinity of the soil studied in relation to the pres- ence of cotton root rot and also of Fusarium wilt. Root rot was found in acid soils (pH 5.5-6.4) as well as in neutral (pH 6.5-7.4) and alkaline soils (pH 7...

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

1928-01-01

126

Rigid motions: Action-angles, relative cohomology and polynomials with roots on the unit circle  

NASA Astrophysics Data System (ADS)

Revisiting canonical integration of the classical solid near a hyperbolic or elliptic uniform rotation, normal canonical coordinates p, q are constructed so that the Hamiltonian becomes a function ("normal form") of x+ = pq or of x- = p2 + q2: the two cases are treated simultaneously distinguishing them, respectively, by a label a = ±, in terms of various power series with coefficients which are shown to be polynomials in a variable r^2_a depending on the inertia moments. The normal forms are derived via the analysis of a relative cohomology problem and shown to be obtainable without reference to the construction of the normal coordinates via elliptic integrals (unlike the derivation of the normal coordinates p, q). Results and conjectures also emerge about the properties of the above polynomials and the location of their roots. In particular a class of polynomials with all roots on the unit circle arises.

Françoise, J.-P.; Garrido, P. L.; Gallavotti, G.

2013-03-01

127

Root gravitropism  

NASA Technical Reports Server (NTRS)

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

Masson, P. H.

1995-01-01

128

Root exudation and rhizoplane bacterial abundance of barley ( Hordeum vulgare L.) in relation to nitrogen fertilization and root growth  

Microsoft Academic Search

The abundance of bacteria in the rhizoplane of barley varieties was investigated at different soil nitrogen levels. Increased\\u000a amendments of nitrogen resulted in higher bacterial numbers in the rhizoplane of barley seedlings of different varieties.\\u000a A negative correlation was found between nitrogen level in the soil and the growth rate of the seedling roots. The effect\\u000a of nitrogen on the

E. Liljeroth; E. Bååth; I. Mathiasson; T. Lundborg

1990-01-01

129

Root cold tolerance of black spruce seedlings: viability tests in relation to survival and regrowth.  

PubMed

Root systems of 6-month-old, cold-hardened, container-grown black spruce seedlings (Picea mariana (Mill.) B.S.P.) were exposed to 0, -5, -10, -15, -20, or -22.5 degrees C. Freezing-induced damage to fine roots, coarse roots and the whole root system was assessed by various viability tests including leakage of electrolytes, leakage of phenolic compounds, water loss, root and shoot water potentials, and live root dry mass. To assess the long-term effects of freezing-induced root damage, seedling survival and regrowth were measured. Leakage of both electrolytes and phenolic compounds differed among fine roots, coarse roots, and whole root systems. In coarse roots and the whole root system, but not in fine roots, leakage of electrolytes, leakage of phenolic compounds, water loss, and root and shoot water potentials were correlated with percentage of live root dry mass which, in turn, was highly correlated with seedling survival and regrowth. Compared with live root dry mass, electrolyte and phenolic leakage, water loss, and root and shoot water potentials were less well correlated with seedling survival and regrowth. Among the viability tests, electrolyte leakage of the whole root system correlated most closely with seedling survival and regrowth. Under freezing conditions that destroyed less than 50% of each seedling's root system, about 70% of the seedlings survived and subsequent growth was little affected, whereas under freezing conditions that destroyed 70% of each seedling's root system, only about 30% of the seedlings survived and subsequent growth was reduced compared with that of undamaged plants. PMID:14759854

Bigras, F J

1997-05-01

130

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. PMID:17921518

Shimamura, Satoshi; Yoshida, Satoshi; Mochizuki, Toshihiro

2007-01-01

131

Root and Nodule Growth in Pisum sativum L. in Relation to Photosynthesis: Analysis Using 13C?labelling  

PubMed Central

The effect of the nitrogen source (gaseous nitrogen, N2, or nitrate ions, NO3–) on the use of carbon (C) for root and nodule growth of pea (Pisum sativum L.) was investigated using 13C?labelling of assimilated CO2 at various stages of growth. Nitrate supply and growing conditions (sowing dates, air CO2 concentration) were varied to alter photosynthetic rates. Nodules are the sink with the highest demand for C in both the vegetative and flowering stages, growing at the expense of shoot and root in the vegetative stage, but only at the expense of roots at flowering. Until flowering, the addition of C into root and nodule biomass was linearly related to pre?existing biomass, thus determining net sink strengths which decreased with root and nodule age. Nodule growth patterns did not depend on the N source, whereas root growth was increased by nitrate when nodule biomass was low. At seed filling, the increase in C of biomass of the root system was no longer related to pre?existing biomass and C was preferentially diverted to roots of plants assimilating nitrate, or to nodules for plants fixing N2. PMID:14507741

VOISIN, A. S.; SALON, C.; JEUDY, C.; WAREMBOURG, F. R.

2003-01-01

132

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

Microsoft Academic Search

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

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

1997-01-01

133

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

E-print Network

ROOTING CHARACTERISTICS OF SLASH PINE (PINUS ELLIOTTII ENGELM. ) IN RELATION TO SOIL FRAGIPANS IN THE FLATWOODS SECTION OF SOUTHEAST TEXAS A Thesis by CHARLES DAVID BATTE Submitted to the Graduate College of Texas ARM University in partial... CHARLES DAVID BATTE Approved as to style and content by: L v /gpfJPZI & r Chairman of Committee ea epartm nt Member Member December 1975 439324 ABSTRACT Rooting Characteristics of Slash Pine (Pinus elliottii Engelm. ) in Relation to Soil...

Batte, Charles David

2012-06-07

134

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

PubMed Central

Gene transcription is constrained by the nucleosomal nature of chromosomal DNA. This nucleosomal barrier is modulated by FACT, a conserved histone-binding heterodimer. FACT mediates transcription-linked nucleosome disassembly and also nucleosome reassembly in the wake of the RNA polymerase II transcription complex, and in this way maintains the repression of ‘cryptic’ promoters found within some genes. Here we focus on a novel mutant version of the yeast FACT subunit Spt16 that supplies essential Spt16 activities but impairs transcription-linked nucleosome reassembly in dominant fashion. This Spt16 mutant protein also has genetic effects that are recessive, which we used to show that certain Spt16 activities collaborate with histone acetylation and the activities of a Bur-kinase/Spt4–Spt5/Paf1C pathway that facilitate transcription elongation. These collaborating activities were opposed by the actions of Rpd3S, a histone deacetylase that restores a repressive chromatin environment in a transcription-linked manner. Spt16 activity paralleling that of HirC, a co-repressor of histone gene expression, was also found to be opposed by Rpd3S. Our findings suggest that Spt16, the Bur/Spt4–Spt5/Paf1C pathway, and normal histone abundance and/or stoichiometry, in mutually cooperative fashion, facilitate nucleosome disassembly during transcription elongation. The recessive nature of these effects of the mutant Spt16 protein on transcription-linked nucleosome disassembly, contrasted to its dominant negative effect on transcription-linked nucleosome reassembly, indicate that mutant FACT harbouring the mutant Spt16 protein competes poorly with normal FACT at the stage of transcription-linked nucleosome disassembly, but effectively with normal FACT for transcription-linked nucleosome reassembly. This functional difference is consistent with the idea that FACT association with the transcription elongation complex depends on nucleosome disassembly, and that the same FACT molecule that associates with an elongation complex through nucleosome disassembly is retained for reassembly of the same nucleosome. PMID:22022426

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

2011-01-01

135

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

136

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

PubMed

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

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

2013-07-01

137

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. PMID:23918389

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

2013-01-01

138

[Effects of exogenous NO3- on cherry root function and enzyme activities related to nitrogen metabolism under hypoxia stress].  

PubMed

A water culture experiment with controlled dissolved oxygen concentration was conducted to explore the effects of exogenous NO3- on the root function and enzyme activities related to nitrogen metabolism of cherry (Prunun cerasus x P. canescens) seedlings under hypoxia stress. Comparing with the control (7.5 mmol NO3- x L(-1)), treatments 15 and 22.5 mmol NO3- x L(-1) made the materials for plant metabolism abundant, ensured the synthesis of enzyme proteins, increased root activity, maintained root respiration, improved the activities of enzymes related to nitrogen metabolism, such as nitrate reductase (NR), glutamine synthethase (GS), and glutamate dehydrogenase (NADH-GDH) in roots, and thereby, supplied enough energy for root respiration and NAD+ to glycolytic pathway, ensured electron transfer, and avoid ammonium toxicity under hypoxia stress. As a result, the injury of hypoxia stress to cherry plant was alleviated. Applying NO3- at the concentration of 22.5 mmol x L(-1) was more advisable. However, NO3- deficiency (0 mmol x L(-1)) showed opposite results. The above results suggested that applying exogenous NO3- to growth medium could regulate cherry root function and nitrogen metabolism, and antagonize the damage of hypoxia stress on cherry roots. PMID:21443020

Feng, Li-guo; Sheng, Li-xi; Shu, Huai-rui

2010-12-01

139

Nitric oxide affecting root growth, lignification and related enzymes in soybean seedlings  

Microsoft Academic Search

This study analyzed the involvement of nitric oxide (NO) in the root lignification of soybean seedlings. To this end, changes\\u000a in root cell viability; phenylalanine ammonia-lyase (PAL) and soluble and cell wall bound peroxidase (POD) activities and\\u000a lignin and hydrogen peroxide (H2O2) contents of soybean roots treated with the NO-donor sodium nitroprusside (SNP) and its relationships with root growth were

Franciele Mara Lucca Zanardo Böhm; Maria de Lourdes Lucio Ferrarese; Daniele Iara Lucca Zanardo; Jose Ronaldo Magalhaes; Osvaldo Ferrarese-Filho

2010-01-01

140

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. PMID:23847638

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

2013-01-01

141

Root gravitropism in maize and Arabidopsis  

NASA Technical Reports Server (NTRS)

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

Evans, Michael L.

1993-01-01

142

Rooting of blue honeysuckle microshoots  

Microsoft Academic Search

Rooting of axillary shoots of two blue honeysuckle forms, Lonicera caerulea f. caerulea and L. caerulea f. edulis, was studied.\\u000a Both in vitro and ex vitro rooting procedures were used, and the effects of mineral and auxin concentrations of the rooting\\u000a media were tested. Reduced mineral nutrient concentrations of modified MS medium allowed more root elongation but did not\\u000a affect

Saila T. Karhu

1997-01-01

143

The Spatially Variable Inhibition by Water Deficit of Maize Root Growth Correlates with Altered Profiles of Proton Flux and Cell Wall pH1  

PubMed Central

Growth of elongating primary roots of maize (Zea mays) seedlings was approximately 50% inhibited after 48 h in aerated nutrient solution under water deficit induced by polyethylene glycol 6000 at ?0.5 MPa water potential. Proton flux along the root elongation zone was assayed by high resolution analyses of images of acid diffusion around roots contacted for 5 min with pH indicator gel. Profiles of root segmental elongation correlated qualitatively and quantitatively (r2 = 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 to 10 mm behind the tip. Associated changes in apoplastic pH inside epidermal cell walls were measured in three defined regions along the root elongation zone by confocal laser scanning microscopy using a ratiometric method. Finally, external acidification of roots was shown to specifically induce a partial reversal of growth inhibition by water deficit in the central region of the elongation zone. These new findings, plus evidence in the literature concerning increases induced by acid pH in wall-extensibility parameters, lead us to propose that the apparently adaptive maintenance of growth 0 to 3 mm behind the tip in maize primary roots under water deficit and the associated inhibition of growth further behind the tip are related to spatially variable changes in proton pumping into expanding cell walls. PMID:15286291

Fan, Ling; Neumann, Peter M.

2004-01-01

144

The action of auxin on plant cell elongation  

Microsoft Academic Search

The review will focus on recent advances in our understanding of the action of auxin on plant cell elongation. Particular emphasis will be placed on the acid growth theory of auxin action and a comparison of auxin action on shoot vs. root tissues. Theories of the action of auxin will be evaluated in view of recent information on auxin dose\\/response

Michael L. Evans; Robert E. Cleland

1985-01-01

145

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. PMID:21969258

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

2011-01-01

146

An auxin transport mechanism restricts positive orthogravitropism in lateral roots.  

PubMed

As soon as a seed germinates, plant growth relates to gravity to ensure that the root penetrates the soil and the shoot expands aerially. Whereas mechanisms of positive and negative orthogravitropism of primary roots and shoots are relatively well understood, lateral organs often show more complex growth behavior. Lateral roots (LRs) seemingly suppress positive gravitropic growth and show a defined gravitropic set-point angle (GSA) that allows radial expansion of the root system (plagiotropism). Despite its eminent importance for root architecture, it so far remains completely unknown how lateral organs partially suppress positive orthogravitropism. Here we show that the phytohormone auxin steers GSA formation and limits positive orthogravitropism in LR. Low and high auxin levels/signaling lead to radial or axial root systems, respectively. At a cellular level, it is the auxin transport-dependent regulation of asymmetric growth in the elongation zone that determines GSA. Our data suggest that strong repression of PIN4/PIN7 and transient PIN3 expression limit auxin redistribution in young LR columella cells. We conclude that PIN activity, by temporally limiting the asymmetric auxin fluxes in the tip of LRs, induces transient, differential growth responses in the elongation zone and, consequently, controls root architecture. PMID:23583551

Rosquete, Michel Ruiz; von Wangenheim, Daniel; Marhavý, Peter; Barbez, Elke; Stelzer, Ernst H K; Benková, Eva; Maizel, Alexis; Kleine-Vehn, Jürgen

2013-05-01

147

Quantitative divergence of the bacterial root microbiota in Arabidopsis thaliana relatives  

PubMed Central

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

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

2014-01-01

148

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

149

Different Relative Orientation of Static and Alternative Magnetic Fields and Cress Roots Direction of Growth Changes Their Gravitropic Reaction  

NASA Astrophysics Data System (ADS)

The following variants of roots location relatively to static and alternative components of magnetic field were studied. At first variant the static magnetic field was directed parallel to the gravitation vector, the alternative magnetic field was directed perpendicular to static one; roots were directed perpendicular to both two fields’ components and gravitation vector. At the variant the negative gravitropysm for cress roots was observed. At second variant the static magnetic field was directed parallel to the gravitation vector, the alternative magnetic field was directed perpendicular to static one; roots were directed parallel to alternative magnetic field. At third variant the alternative magnetic field was directed parallel to the gravitation vector, the static magnetic field was directed perpendicular to the gravitation vector, roots were directed perpendicular to both two fields components and gravitation vector; At forth variant the alternative magnetic field was directed parallel to the gravitation vector, the static magnetic field was directed perpendicular to the gravitation vector, roots were directed parallel to static magnetic field. In all cases studied the alternative magnetic field frequency was equal to Ca ions cyclotron frequency. In 2, 3 and 4 variants gravitropism was positive. But the gravitropic reaction speeds were different. In second and forth variants the gravitropic reaction speed in error limits coincided with the gravitropic reaction speed under Earth’s conditions. At third variant the gravitropic reaction speed was slowed essentially.

Sheykina, Nadiia; Bogatina, Nina

150

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. PMID:22151917

2011-01-01

151

Influence of irradiance on water relations and carbon flux during rooting of Shorea leprosula leafy stem cuttings.  

PubMed

Single-node leafy stem cuttings of Shorea leprosula Miq. were subjected to a high, intermediate or low irradiance treatment for 16 weeks in an enclosed mist propagation system. Before rooting, maximum photosynthesis of the cuttings occurred at an irradiance of 400 micro mol m(-2) s(-1). Although none of the irradiance treatments affected the number of roots produced per cutting, the numbers of cuttings that formed roots were 50 and 30% in the high irradiance (diurnal range of 0-658 micro mol m(-2) s(-1)) and low irradiance (diurnal range of 0-98 micro mol m(-2) s(-1)) treatments, respectively, compared with 62% in the intermediate irradiance treatment (diurnal range of 0-360 micro mol m(-2) s(-1)). Low rooting frequency of cuttings in the high irradiance treatment was associated with water deficits (maximum leaf-to-air vapor pressure deficit (VPD) = 3.6 kPa), whereas cuttings in the low irradiance treatment had a low rooting frequency because they were below the light compensation point most of the time. In the intermediate irradiance treatment, cuttings withstood a daily maximum VPD of 1-2 kPa and recovered overnight from the previous day's deficit, as indicated by higher relative water content (RWC) and stomatal conductance (g(s)) in the morning than in the previous afternoon and evening. Higher RWC and g(s) of cuttings in all treatments on Days 14 and 21 compared with Day 8 probably indicated recovery from water deficit following severance and insertion of the cuttings in rooting medium. There were negative relationships between stem volume of cuttings and both number of cuttings that rooted and number of roots per cutting. PMID:14759836

Aminah, H; McP Dick, J; Grace, J

1997-07-01

152

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. PMID:12226427

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

1996-01-01

153

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

154

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

PubMed

We used a video digitizer system to measure surface extension and curvature in gravistimulated primary roots of maize (Zea mays L.). Downward curvature began about 25 +/- 7 min after gravistimulation and resulted from a combination of enhanced growth along the upper surface and reduced growth along the lower surface relative to growth in vertically oriented controls. The roots curved at a rate of 1.4 +/- 0.5 degrees min-1 but the pattern of curvature varied somewhat. In about 35% of the samples the roots curved steadily downward and the rate of curvature slowed as the root neared 90 degrees. A final angle of about 90 degrees was reached 110 +/- 35 min after the start of gravistimulation. In about 65% of the samples there was a period of backward curvature (partial reversal of curvature) during the response. In some cases (about 15% of those showing a period of reverse bending) this period of backward curvature occurred before the root reached 90 degrees. Following transient backward curvature, downward curvature resumed and the root approached a final angle of about 90 degrees. In about 65% of the roots showing a period of reverse curvature, the roots curved steadily past the vertical, reaching maximum curvature about 205 +/- 65 min after gravistimulation. The direction of curvature then reversed back toward the vertical. After one or two oscillations about the vertical the roots obtained a vertical orientation and the distribution of growth within the root tip became the same as that prior to gravistimulation. The period of transient backward curvature coincided with and was evidently caused by enhancement of growth along the concave and inhibition of growth along the convex side of the curve, a pattern opposite to that prevailing in the earlier stages of downward curvature. There were periods during the gravitropic response when the normally unimodal growth-rate distribution within the elongation zone became bimodal with two peaks of rapid elongation separated by a region of reduced elongation rate. This occurred at different times on the convex and concave sides of the graviresponding root. During the period of steady downward curvature the elongation zone along the convex side extended farther toward the tip than in the vertical control. During the period of reduced rate of curvature, the zone of elongation extended farther toward the tip along the concave side of the root. The data show that the gravitropic response pattern varies with time and involves changes in localized elongation rates as well as changes in the length and position of the elongation zone. Models of root gravitropic curvature based on simple unimodal inhibition of growth along the lower side cannot account for these complex growth patterns. PMID:11538269

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

1991-02-01

155

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

156

Root gravitropism: a complex response to a simple stimulus?  

Microsoft Academic Search

Roots avoid depleting their immediate environment of essential nutrients by continuous growth. Root growth is directed by environmental cues, including gravity. Gravity sensing occurs mainly in the columella cells of the root cap. Upon reorientation within the gravity field, the root-cap amyloplasts sediment, generating a physiological signal that promotes the development of a curvature at the root elongation zones. Recent

Elizabeth Rosen; Rujin Chen; Patrick H Masson

1999-01-01

157

Genetics of Cotton Fiber Elongation  

E-print Network

means analysis (GMA). Findings from this study should lay the foundation for future breeding work in cotton fiber elongation. Of the seven distinctive upland parents used for the diallel study, general combining ability was far more prominent than...

Ng, Eng Hwa

2013-05-29

158

Two SCARECROW-LIKE genes are induced in response to exogenous auxin in rooting-competent cuttings of distantly related forest species.  

PubMed

We characterized SCARECROW-LIKE genes induced by auxin in rooting-competent cuttings of two distantly related forest species (Pinus radiata D. Don and Castanea sativa Mill.) before the activation of cell division that results in adventitious root formation. The predicted protein sequences contain domains characteristic of the GRAS protein family and show a strong similarity to the SCARECROW-LIKE proteins, indicating conserved functions of these proteins. Quantitative RT-PCR analysis showed that these genes are expressed at relatively high levels in roots. Induction of increased mRNA levels in rooting-competent cuttings of both species in response to exogenous auxin was observed within the first 24 h of the root induction process, a time when cell reorganization takes place, but before the resumption of cell division and the appearance of adventitious root primordia. These results suggest that SCARECROW-LIKE genes play a role during the earliest stages of adventitious root formation. PMID:17669736

Sánchez, Conchi; Vielba, Jesús M; Ferro, Enrique; Covelo, Guillermo; Solé, Alicia; Abarca, Dolores; de Mier, Belén S; Díaz-Sala, Carmen

2007-10-01

159

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

PubMed

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

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

2013-10-01

160

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

PubMed

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

Kamaluddin, M; Zwiazek, Janusz J

2004-10-01

161

PACSIN1, a Tau-interacting protein, regulates axonal elongation and branching by facilitating microtubule instability.  

PubMed

Tau is a major member of the neuronal microtubule-associated proteins. It promotes tubulin assembly and stabilizes axonal microtubules. Previous studies have demonstrated that Tau forms cross-bridges between microtubules, with some particles located on cross-bridges, suggesting that some proteins interact with Tau and might be involved in regulating Tau-related microtubule dynamics. This study reports that PACSIN1 interacts with Tau in axon. PACSIN1 blockade results in impaired axonal elongation and a higher number of primary axonal branches in mouse dorsal root ganglia neurons, which is induced by increasing the binding ability of Tau to microtubules. In PACSIN1-blocked dorsal root ganglia neurons, a greater amount of Tau is inclined to accumulate in the central domain of growth cones, and it promotes the stability of the microtubule network. Taken together, these results suggest that PACSIN1 is an important Tau binding partner in regulating microtubule dynamics and forming axonal plasticity. PMID:23035120

Liu, Yingying; Lv, Kaosheng; Li, Zenglong; Yu, Albert C H; Chen, Jianguo; Teng, Junlin

2012-11-16

162

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

163

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

PubMed

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 (RGR). There is little evidence, after the effects of RGR are removed, that the fast versus slow foraging theory is correct. In a pot study, we evaluated foraging of four grass species that differed in RGR: one fast-growing annual species, Bromus diandrus, two intermediate-growing species, annual Bromus hordeaceus and perennial Elymus glaucus, and one slow-growing perennial species, Nassella pulchra. We harvested plants either at a common time (plants varied in size) or at a common leaf number (plants similar size, surrogate for common biomass). By evaluating species at a common time, RGR influenced foraging. Conversely, by evaluating species at a common leaf number, foraging could be evaluated independent of RGR. When RGR was allowed to contribute to foraging (common time harvest), foraging and RGR were positively correlated. B. diandrus (fast RGR) foraged to a greater extent than did E. glaucus (intermediate RGR) and N. pulchra (slow RGR). E. glaucus (intermediate RGR) foraged to a greater extent than N. pulchra (slow RGR). Root growth within nutrient-rich microsites was due to significant increases in RBD, not to modifications of SRL or BF. However, when RGR was not allowed to influence foraging (common leaf number harvest), none of the four species significantly enhanced RLD in nutrient-rich compared to control microsites. This suggests that RGR strongly influenced the ability of these grass species to forage and also supports the need to evaluate plastic root traits independent of RGR. PMID:12750991

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

2003-08-01

164

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

PubMed Central

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

2013-01-01

165

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

Microsoft Academic Search

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

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

1998-01-01

166

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

Microsoft Academic Search

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

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

167

Effects of Plant Root Oxygen Deprivation in Relation to Water and Nitrate Uptake for Rose  

E-print Network

cellular respiration. Plants absorb oxygen through their roots. Past research has shown that reducing concentration in the rootzone became a limiting factor on the plants' ability to perform cellular respiration a limiting factor on cellular respiration. INTRODUCTION The commercial use of hydroponics for production

Lieth, J. Heinrich

168

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

EPA Science Inventory

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

169

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

EPA Science Inventory

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

170

Variations between rice cultivars in iron and manganese plaque on roots and the relation with plant cadmium uptake.  

PubMed

To understand certain mechanisms causing variations between rice cultivars with regard to cadmium uptake and tolerance, pot soil experiments were conducted with two rice cultivars of different genotypes under different soil Cd levels. The relationships between plant Cd uptake and iron/manganese (Fe/Mn) plaque formation on roots were investigated. The results showed that rice cultivars differed markedly in Cd uptake and tolerance. Under soil Cd treatments, Cd concentrations and accumulations in the cultivar Shanyou 63 (the genotype indica) were significantly higher than those in the cultivar Wuyunjing 7 (the genotype japonica) (P < 0.01, or P < 0.05), and Shanyou 63 was more sensitive to Cd toxicity than Wuyunjing 7. The differences between the rice cultivars were the largest at relatively low soil Cd level (i.e., 10 mg/kg). Fe concentrations in dithionite-citrate-bicarbonate root extracts of Shanyou 63 were generally lower than that of Wuyunjing 7, and the difference was the most significant under the treatment of 10 mg Cd/kg soil. The results indicated that the formation of iron plaque on rice roots could act as a barrier to soil Cd toxicity, and may be a "buffer" or a "reservoir" which could reduce Cd uptake into rice roots. And the plaque may contribute, to some extent, to the genotypic differences of rice cultivars in Cd uptake and tolerance. PMID:21174997

Liu, Jianguo; Cao, Changxun; Wong, Minghung; Zhang, Zhijun; Chai, Yuhong

2010-01-01

171

Magnesium availability regulates the development of root hairs in Arabidopsis thaliana (L.) Heynh.  

PubMed

Root hairs are reported to be plastic in response to nutrient supply, but relatively little is known about their development in response to magnesium (Mg) availability. Here, we showed that development of root hairs of Arabidopsis decreased progressively with increasing Mg supply, which was related to the initiation of new trichoblast files and likelihood of trichoblasts to form hairs. Tip-focused reactive oxygen species (ROS) and cytosolic Ca(2+) concentrations [(Ca(2+) )c] during elongation of root hairs were enhanced under low Mg but decreased under high Mg. Under low Mg, application of diphenylene iodonium (DPI) or BAPTA [1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid] blocked the enhanced development of root hairs and the opposite was true when the plants under high Mg were treated with phenazine methosulphate (PMS), methyl viologen (MV) or CaCl2 . Furthermore, Mg availability did not alter root hair growth in rhd2-1 mutant that contains lower levels of ROS and cytosolic [Ca(2+) ]c. Transcriptome data and qPCR results revealed a greater fraction of morphogenetic H-genes, and cell wall organization genes were up-regulated by low Mg but down-regulated by high Mg. Our data suggest a profound effect of Mg supply on the development of root hairs in Arabidopsis, through the characterized Ca(2+) and ROS signals that modulate the elongation of root hairs and the expression of root-hair morphogenetic genes. PMID:24851702

Niu, Yaofang; Chai, Rushan; Liu, Lijuan; Jin, Gulei; Liu, Miao; Tang, Caixian; Zhang, Yongsong

2014-12-01

172

‘Square root’ of the Maxwell Lagrangian versus confinement in general relativity  

NASA Astrophysics Data System (ADS)

We employ the 'square root' of the Maxwell Lagrangian (i.e. ?{F??F}), coupled with gravity to search for the possible linear potentials which are believed to play role in confinement. It is found that in the presence of magnetic charge no confining potential exists in such a model. Confining field solutions are found for radial geodesics in pure electrically charged Nariai-Bertotti-Robinson (NBR)-type spacetime with constant scalar curvature. Recently, Guendelman, Kaganovich, Nissimov and Pacheva (2011) [7] have shown that superposed square root with standard Maxwell Lagrangian yields confining potentials in spherically symmetric spacetimes with new generalized Reissner-Nordström-de Sitter/anti-de Sitter black hole solutions. In NBR spacetimes we show that confining potentials exist even when the standard Maxwell Lagrangian is relaxed.

Mazharimousavi, S. Habib; Halilsoy, M.

2012-04-01

173

Ultrastructure of Rhizobium japonicum in relation to its attachment to root hairs.  

PubMed Central

In Rhizobium japonicum strain Nitragin 61A76, morphologically distinct types of bacteria were found to occur in yeast extract-mannitol broth cultures, at both mid-log and stationary phases. Of these only the capsular form, characterized by a smooth cell envelope, storage granules (glycogen and poly-beta-hydroxybutyric acid), and an amorphous extracellular capsule, bound soybean lectin. The binding site was localized in the capsular material. Less than 1% of the bacterial population differentiated into these capsular forms, which were also able to attach to the soybean root hair surface. Images PMID:565352

Bal, A K; Shantharam, S; Ratnam, S

1978-01-01

174

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

NASA Astrophysics Data System (ADS)

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

Graf, Frank; Frei, Martin

2013-04-01

175

Gibberellin Biosynthesis Mutations and Root Development in Pea  

PubMed Central

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

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

2001-01-01

176

Plant high tolerance to excess manganese related with root growth, manganese distribution and antioxidative enzyme activity in three grape cultivars.  

PubMed

The cuttings of grape (Vitis vinifera Linn.) were exposed to Hoagland's solution containing five different manganese (Mn) concentrations to investigate Mn toxicity and the possible detoxifying responses. Three genotypes (i.e. cultivars Combiner, Jingshou and Shuijing) were used in present study. The results showed that grape species is highly tolerant to excess Mn. The plant growth is stimulated by as high as 15 or 30 mM Mn, and then depressed by higher Mn levels. The grape tolerance to excess Mn is related with plant capacity to keep constant or increased root growth as well as to keep high root activity. Also, the grape could employ some effective but intraspecific strategies to detoxify cellular Mn stress by excluding excess Mn out of leaf tissues or by enhancing antioxidative capacity. On the other hand, the present study showed that there existed different (or contrast) distribution pattern for excess Mn in grape. Majority of Mn was transferred and accumulated in the above-ground part in Combiner while Jingshou stored most Mn in root systems. For the first time our result showed the extreme tolerance and contrast performance at Mn translocation in an important fruit species with revealed genomic information. PMID:21075449

Mou, Dongling; Yao, Yinan; Yang, Yongqing; Zhang, Yuanming; Tian, Changyan; Achal, Varenyam

2011-05-01

177

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

PubMed

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

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

2011-02-01

178

Mechanism of Amyloid-? Fibril Elongation.  

PubMed

Amyloid-? is an intrinsically disordered protein that forms fibrils in the brains of patients with Alzheimer's disease. To explore factors that affect the process of fibril growth, we computed the free energy associated with disordered amyloid-? monomers being added to growing amyloid fibrils using extensive molecular dynamics simulations coupled with umbrella sampling. We find that the mechanisms of A?40 and A?42 fibril elongation have many features in common, including the formation of an obligate on-pathway ?-hairpin intermediate that hydrogen bonds to the fibril core. In addition, our data lead to new hypotheses for how fibrils may serve as secondary nucleation sites that can catalyze the formation of soluble oligomers, a finding in agreement with recent experimental observations. These data provide a detailed mechanistic description of amyloid-? fibril elongation and a structural link between the disordered free monomer and the growth of amyloid fibrils and soluble oligomers. PMID:25330398

Gurry, Thomas; Stultz, Collin M

2014-11-11

179

Capturing Arabidopsis Root Architecture Dynamics with root-fit Reveals Diversity in Responses to Salinity.  

PubMed

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

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

2014-11-01

180

Arbuscular mycorrhizal symbiosis increases relative apoplastic water flow in roots of the host plant under both well-watered and drought stress conditions  

PubMed Central

Background and Aims The movement of water through mycorrhizal fungal tissues and between the fungus and roots is little understood. It has been demonstrated that arbuscular mycorrhizal (AM) symbiosis regulates root hydraulic properties, including root hydraulic conductivity. However, it is not clear whether this effect is due to a regulation of root aquaporins (cell-to-cell pathway) or to enhanced apoplastic water flow. Here we measured the relative contributions of the apoplastic versus the cell-to-cell pathway for water movement in roots of AM and non-AM plants. Methods We used a combination of two experiments using the apoplastic tracer dye light green SF yellowish and sodium azide as an inhibitor of aquaporin activity. Plant water and physiological status, root hydraulic conductivity and apoplastic water flow were measured. Key Results Roots of AM plants enhanced significantly relative apoplastic water flow as compared with non-AM plants and this increase was evident under both well-watered and drought stress conditions. The presence of the AM fungus in the roots of the host plants was able to modulate the switching between apoplastic and cell-to-cell water transport pathways. Conclusions The ability of AM plants to switch between water transport pathways could allow a higher flexibility in the response of these plants to water shortage according to the demand from the shoot. PMID:22294476

Barzana, Gloria; Aroca, Ricardo; Paz, Jose Antonio; Chaumont, Francois; Martinez-Ballesta, Mari Carmen; Carvajal, Micaela; Ruiz-Lozano, Juan Manuel

2012-01-01

181

Extracellular Proteins in Pea Root Tip and Border Cell Exudates1[OA  

PubMed Central

Newly generated plant tissue is inherently sensitive to infection. Yet, when pea (Pisum sativum) roots are inoculated with the pea pathogen, Nectria haematococca, most newly generated root tips remain uninfected even though most roots develop lesions just behind the tip in the region of elongation. The resistance mechanism is unknown but is correlated spatially with the presence of border cells on the cap periphery. Previously, an array of >100 extracellular proteins was found to be released while border cell separation proceeds. Here we report that protein secretion from pea root caps is induced in correlation with border cell separation. When this root cap secretome was proteolytically degraded during inoculation of pea roots with N. haematococca, the percentage of infected root tips increased from 4% ± 3% to 100%. In control experiments, protease treatment of conidia or roots had no effect on growth and development of the fungus or the plant. A complex of >100 extracellular proteins was confirmed, by multidimensional protein identification technology, to comprise the root cap secretome. In addition to defense-related and signaling enzymes known to be present in the plant apoplast were ribosomal proteins, 14-3-3 proteins, and others typically associated with intracellular localization but recently shown to be extracellular components of microbial biofilms. We conclude that the root cap, long known to release a high molecular weight polysaccharide mucilage and thousands of living cells into the incipient rhizosphere, also secretes a complex mixture of proteins that appear to function in protection of the root tip from infection. PMID:17142479

Wen, Fushi; VanEtten, Hans D.; Tsaprailis, George; Hawes, Martha C.

2007-01-01

182

Changes in root cap pH are required for the gravity response of the Arabidopsis root  

NASA Technical Reports Server (NTRS)

Although the columella cells of the root cap have been identified as the site of gravity perception, the cellular events that mediate gravity signaling remain poorly understood. To determine if cytoplasmic and/or wall pH mediates the initial stages of root gravitropism, we combined a novel cell wall pH sensor (a cellulose binding domain peptide-Oregon green conjugate) and a cytoplasmic pH sensor (plants expressing pH-sensitive green fluorescent protein) to monitor pH dynamics throughout the graviresponding Arabidopsis root. The root cap apoplast acidified from pH 5.5 to 4.5 within 2 min of gravistimulation. Concomitantly, cytoplasmic pH increased in columella cells from 7.2 to 7.6 but was unchanged elsewhere in the root. These changes in cap pH preceded detectable tropic growth or growth-related pH changes in the elongation zone cell wall by 10 min. Altering the gravity-related columella cytoplasmic pH shift with caged protons delayed the gravitropic response. Together, these results suggest that alterations in root cap pH likely are involved in the initial events that mediate root gravity perception or signal transduction.

Fasano, J. M.; Swanson, S. J.; Blancaflor, E. B.; Dowd, P. E.; Kao, T. H.; Gilroy, S.

2001-01-01

183

Girdling Affects Carbohydrate?related Gene Expression in Leaves, Bark and Roots of Alternate?bearing Citrus Trees  

PubMed Central

Effects of girdling on carbohydrate status and carbohydrate?related gene expression in citrus trees were investigated. Alternate?bearing ‘Murcott’ (a Citrus reticulata hybrid of unknown origin) trees were girdled during autumn (25 Sep. 2001) and examined 10 weeks later. Girdling brought about carbohydrate (soluble sugar and starch) accumulation in leaves and shoot bark above the girdle, in trees during their fruitless, ‘off’ year. Trees during their heavy fruit load, ‘on’ year did not accumulate carbohydrates above the girdle due to the high demand for carbohydrates by the developing fruit. Girdling caused a strong decline in soluble sugar and starch concentrations in organs below the girdle (roots), in both ‘on’ and ‘off’ trees. Expression of STPH?L and STPH?H (two isoforms of starch phosphorylase), Agps (ADP?glucose pyrophosphorylase, small subunit), AATP (plastidic ADP/ATP transporter), PGM?C (phosphoglucomutase) and CitSuS1 (sucrose synthase), all of which are associated with starch accumulation, was studied. It was found that gene expression is related to starch accumulation in all ‘off’ tree organs. RNA levels of all the genes examined were high in leaves and bark that accumulated high concentrations of starch, and low in roots with declining starch concentrations. It may be hypothesized that changes in specific sugars signal the up? and down?regulation of genes involved in starch synthesis. PMID:12763756

LI, CHUN?YAO; WEISS, DAVID; GOLDSCHMIDT, ELIEZER E.

2003-01-01

184

Kinematics and Dynamics of Sorghum (Sorghum bicolor L.) Leaf Development at Various Na/Ca Salinities (I. Elongation Growth).  

PubMed Central

In many salt-sensitive species, elevated concentrations of Ca in the root growth media ameliorate part of the shoot growth reduction caused by NaCl stress. The physiological mechanisms by which Ca exerts protective effects on leaf growth are still not understood. Understanding growth inhibition caused by a stress necessitates locating the leaf expansion region and quantifying the profile of the growth reduction. This will enable comparisons and correlations with spatial gradients of probable physiologically inhibiting factors. In this work we applied the methods of growth kinematics to analyze the effects of elevated Ca concentrations on the spatial and temporal distributions of growth within the intercalary expanding region of salinized sorghum (Sorghum bicolor [L.] Moench, cv NK 265) leaves. NaCl (100 mM) caused a decrease in leaf elongation rate by shortening the leaf growing zone by 20%, as well as reducing the peak value of the longitudinal relative elemental growth rate (REG rate). Increasing the Ca concentrations from 1 to 10 mM restored the length of the growing zone of both emerged and unemerged salinized leaves and increased the peak value of the REG rate. The beneficial effects of supplemental Ca were, however, more pronounced in leaves after their appearance above the whorl of encircling older leaf sheaths. Elevated Ca then resulted in a peak value of REG rate higher than in the salinized leaves. The peak value of unemerged leaves was not increased, although it was maintained over a longer distance. The duration of elongation growth associated with a cell during its displacement from the leaf base was longer in salinized than control leaves, despite the fact that the elongation zone was shorter in salinity. Although partially restoring the length of the elongation region, supplemental Ca had no effect on the age of cessation of growth. Elongation of a tissue element, therefore, ceased when a cellular element reached a certain age and not a specific distance from the leaf base. PMID:12232005

Bernstein, N.; Lauchli, A.; Silk, W. K.

1993-01-01

185

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 PMID:16660856

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

1979-01-01

186

Of spiders and elongated spots  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

187

Aluminium-induced alteration of ion homeostasis in root tip vacuoles of two maize varieties differing in Al tolerance.  

PubMed

Root elongation is a primary target of Al toxicity in plants. The objective of this study was to see whether Al-induced disturbance of ion homeostasis is related to the inhibition of root elongation. For this purpose, root growth rate, free cytoplasmic calcium (Ca²+) and vacuolar content of phosphate (P(i)), potassium (K+), nitrate (NO??) and malate, as well as malate and citrate exudation and nitrate reductase activity were analysed in tips of two Zea mays L. varieties differing in Al resistance. Aluminium treatment affected root growth and cytoplasmic Ca²+ in the Al sensitive variety Bakero, but not in the Al tolerant variety Sikuani. However, both varieties suffered Al-induced decrease of vacuolar K+, and phosphate concentrations. Vacuolar malate concentrations were more affected by Al in Bakero than in Sikuani. Vacuolar nitrate concentrations increased upon Al exposure in both varieties. Only in Sikuani rhizosphere, pH slightly increased upon Al exposure. Our data are consistent with the hypothesis that disturbance of Ca²+ homeostasis is an early event in the Al toxicity syndrome. However, Al-induced alterations of the root tip homeostasis of major ions seem unrelated to Al-induced inhibition of root elongation. PMID:21421422

Garzón, Teresa; Gunsé, Benet; Moreno, Ana Rodrigo; Tomos, A Deri; Barceló, Juan; Poschenrieder, Charlotte

2011-05-01

188

Strigolactones Effects on Root Growth  

NASA Astrophysics Data System (ADS)

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

Koltai, Hinanit

2012-07-01

189

Nitrogen- and Storage-affected Carbohydrate Partitioning in High-light-adapted Pelargonium Cuttings in Relation to Survival and Adventitious Root Formation under Low Light  

PubMed Central

• Background and Aims The aim of this study was to determine the role of nitrogen- and storage-affected carbohydrate availability in rooting of pelargonium cuttings, focusing on the environmental conditions of stock plant cultivation at low latitudes, transport of cuttings, and rooting under the low light that prevails during the winter rooting period in Central European greenhouses. • Methods Carbohydrate partitioning in high-light-adapted cuttings of the cultivar ‘Isabell’ was studied in relation to survival and adventitious root formation under low light. Effects of a graduated supply of mineral nitrogen to stock plants and of cutting storage were examined. • Key Results Nitrogen deficiency raised starch levels in excised cuttings, whereas the concentrations of glucose and total sugars in leaves and the basal stem were positively correlated with internal total nitrogen (Nt). Storage reduced starch to trace levels in all leaves, but sugar levels were only reduced in tissues of non-nitrogen deficient cuttings. Sugars accumulated in the leaf lamina of stored cuttings during the rooting period, whereas carbohydrates were simultaneously exhausted in all other cutting parts including the petioles, thereby promoting leaf senescence. The positive correlation between initial Nt and root number disappeared after storage. Irrespectively of storage, higher pre-rooting leaf glucose promoted subsequent sugar accumulation in the basal stem and final root number. The positive relationships between initial sugar levels in the stems with cutting survival and in leaves with root formation under low light were confirmed in a sample survey with 21 cultivars provided from different sources at low latitudes. • Conclusions The results indicate that adventitious rooting of pelargonium cuttings can be limited by the initial amount of nitrogen reserves. However, this relationship reveals only small plasticity and is superimposed by a predominant effect of carbohydrate availability that depends on the initial leaf sugar levels, when high-light adaptation and low current light conditions impair net carbon assimilation. PMID:15509634

DRUEGE, U.; ZERCHE, S.; KADNER, R.

2004-01-01

190

From Individual Leaf Elongation to Whole Shoot Leaf Area Expansion: a Comparison of Three Aegilops and Two Triticum Species  

PubMed Central

• Background and Aims Rapid leaf area expansion is a desirable trait in the early growth stages of cereal crops grown in low?rainfall areas. In this study, the traits associated with inherent variation in early leaf area expansion rates have been investigated in two wheat species (Triticum aestivum and T. durum) and three of its wild relatives (Aegilops umbellulata, A. caudata and A. tauschii) to find out whether the Aegilops species have a faster leaf area expansion in their early developmental stage than some of the current wheat species. • Methods Growth of individual leaves, biomass allocation, and gas exchange were measured on hydroponically grown plants for 4 weeks. • Key Results Leaf elongation rate (LER) was strongly and positively correlated with leaf width but not with leaf elongation duration (LED). The species with more rapidly elongating leaves showed a faster increase with leaf position in LER, leaf width and leaf area, higher relative leaf area expansion rates, and more biomass allocation to leaf sheaths and less to roots. No differences in leaf appearance rate were found amongst the species. • Conclusions Aegilops tauschii was the only wild species with rapid leaf expansion rates similar to those of wheat, and it achieved the highest photosynthetic rates, making it an interesting species for further study. PMID:15155374

BULTYNCK, LIEVE; TER STEEGE, MARGREET W.; SCHORTEMEYER, MARCUS; POOT, PIETER; LAMBERS, HANS

2004-01-01

191

RETINOBLASTOMA-RELATED Protein Stimulates Cell Differentiation in the Arabidopsis Root Meristem by Interacting with Cytokinin Signaling[W  

PubMed Central

Maintenance of mitotic cell clusters such as meristematic cells depends on their capacity to maintain the balance between cell division and cell differentiation necessary to control organ growth. In the Arabidopsis thaliana root meristem, the antagonistic interaction of two hormones, auxin and cytokinin, regulates this balance by positioning the transition zone, where mitotically active cells lose their capacity to divide and initiate their differentiation programs. In animals, a major regulator of both cell division and cell differentiation is the tumor suppressor protein RETINOBLASTOMA. Here, we show that similarly to its homolog in animal systems, the plant RETINOBLASTOMA-RELATED (RBR) protein regulates the differentiation of meristematic cells at the transition zone by allowing mRNA accumulation of AUXIN RESPONSE FACTOR19 (ARF19), a transcription factor involved in cell differentiation. We show that both RBR and the cytokinin-dependent transcription factor ARABIDOPSIS RESPONSE REGULATOR12 are required to activate the transcription of ARF19, which is involved in promoting cell differentiation and thus root growth. PMID:24285791

Perilli, Serena; Perez-Perez, Jose Manuel; Di Mambro, Riccardo; Peris, Cristina Llavata; Diaz-Trivino, Sara; Del Bianco, Marta; Pierdonati, Emanuela; Moubayidin, Laila; Cruz-Ramirez, Alfredo; Costantino, Paolo; Scheres, Ben; Sabatini, Sabrina

2013-01-01

192

RETINOBLASTOMA-RELATED protein stimulates cell differentiation in the Arabidopsis root meristem by interacting with cytokinin signaling.  

PubMed

Maintenance of mitotic cell clusters such as meristematic cells depends on their capacity to maintain the balance between cell division and cell differentiation necessary to control organ growth. In the Arabidopsis thaliana root meristem, the antagonistic interaction of two hormones, auxin and cytokinin, regulates this balance by positioning the transition zone, where mitotically active cells lose their capacity to divide and initiate their differentiation programs. In animals, a major regulator of both cell division and cell differentiation is the tumor suppressor protein RETINOBLASTOMA. Here, we show that similarly to its homolog in animal systems, the plant RETINOBLASTOMA-RELATED (RBR) protein regulates the differentiation of meristematic cells at the transition zone by allowing mRNA accumulation of AUXIN RESPONSE FACTOR19 (ARF19), a transcription factor involved in cell differentiation. We show that both RBR and the cytokinin-dependent transcription factor ARABIDOPSIS RESPONSE REGULATOR12 are required to activate the transcription of ARF19, which is involved in promoting cell differentiation and thus root growth. PMID:24285791

Perilli, Serena; Perez-Perez, José Manuel; Di Mambro, Riccardo; Peris, Cristina Llavata; Díaz-Triviño, Sara; Del Bianco, Marta; Pierdonati, Emanuela; Moubayidin, Laila; Cruz-Ramírez, Alfredo; Costantino, Paolo; Scheres, Ben; Sabatini, Sabrina

2013-11-01

193

Foliar leaching and root uptake of Ca, Mg and K in relation to acid fog effects on Douglas Fir  

SciTech Connect

The impact of acid fog on foliar leaching and root uptake of Ca, Mg, and K by Douglas-fir (Pseudotsuga menziesii) seedlings was examined. In a factorial experiment, 1-year old seedlings were grown in a solution culture at two levels of nutrient availability (low and moderate) and exposed twice a week (4 hr per event) for 12 weeks to fog at pH 5.6 or pH 3.1. Throughfall enrichment of Ca, Mg and K was determined from drip collectors at the base of each seedling and root uptake rates for trees under the moderate nutrient regime were evaluated by monitoring nutrient solution depletion. Throughfall enrichment was higher in the pH 3.1 fog than the pH 5.6 fog but much of the enrichment appeared to be wash off of precipitate from previous fogs. The amounts of nutrients coming off of the foliage with the low pH fog were small relative to the daily uptake rates. Foliar concentrations of K and Mg at the end of the exposures were lower under the low nutrient regime but were not affected by fog pH. Comparisons of wax weight and examinations of epicuticular wax by electron microscopy did not indicate a significant impact from exposure to the low pH fog.

Turner, D.P.; Tingey, D.T.

1990-01-01

194

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

NASA Technical Reports Server (NTRS)

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

Ng, Y. K.; Moore, R.

1985-01-01

195

Conduction velocity is related to morphological cell type in rat dorsal root ganglion neurones.  

PubMed Central

Combining intracellular recording and dye-injection techniques permitted direct correlation of neuronal soma size with peripheral nerve conduction velocity in individual neurones of the L4 dorsal root ganglion (d.r.g.) of the anaesthetized 5-8-week-old rat. The conduction velocities fell into two main groups; those greater than 14 m/s (A alpha and beta fibres) and those less than 8 m/s (A delta and C fibres). Fibres with conduction velocities in the A delta range (2.2-8 m/s) in the sciatic nerve between the sciatic notch and the neuronal soma in the d.r.g. often conducted more slowly, that is in the C-fibre range (less than 1.4 m/s), in the periphery from the tibial nerve to the sciatic notch. For the fast-conducting myelinated afferents, there was a loose positive correlation between cell size and the conduction velocity of the peripheral axon, whereas a clearer positive correlation existed between neuronal cell size and axonal conduction velocity both for A delta- and for C-fibre afferents. The relationship of the cell cross-sectional area (measured at the nucleolar level), to the cell volume for each neuronal soma was similar for the different conduction velocity groups. The somata of the fast-conducting myelinated A alpha and A beta fibres had a similar mean and range of cross-sectional areas to those of the large light cell population. The somata with A delta and C fibres were of a more uniform size and were restricted to the smaller cells within the ganglia. The mean and range of cross-sectional areas of the C cells was similar to those of the small dark cell population. A delta somata had a larger mean and range of cell sizes than those of the small dark cell population. The relationships of peripheral axon type to the morphological cell types are discussed. Images Plate 1 PMID:3999040

Harper, A A; Lawson, S N

1985-01-01

196

Distinct structure-activity relations for stimulation of 45Ca uptake and for high affinity binding in cultured rat dorsal root ganglion neurons and dorsal root ganglion membranes  

Microsoft Academic Search

The [3H]resiniferatoxin (RTX) binding assay using membrane preparations has been used to identify and characterize the vanilloid receptors in the central and peripheral nervous system of different species. In the present study, using cultured adult rat dorsal root ganglion neurons either in suspension or attached to the tissue culture plates, we developed an assay to measure specific [3H]RTX binding by

Geza Acs; Jeewoo Lee; Victor E. Marquez; Peter M. Blumberg

1996-01-01

197

The effect of ethylene on root growth of Zea mays seedlings  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

198

Restored river corridors: first results on the effects of flow variability on vegetation cuttings survival rate and related root architecture  

NASA Astrophysics Data System (ADS)

Understanding and predicting the evolution of river alluvial bed forms toward a vegetated or a non-vegetated morphology have important implications for restored river corridors and the related ecosystem functioning (see also Schäppi et al, this session). Vegetation recruitment and growth on non-cohesive material of river corridors, such as gravel bars and islands of braided river, depend on the ability of roots to develop and anchor efficiently such to resist against flow erosion. In this work, we study the interannual morphological evolution of a gravel bar island, the survival rate and the growth of a number of plots with different density and orientation of transplanted cuttings (Salix Alba), the space and time dynamics of which depend on erosion and deposition processes due to floods. Our purpose is to identify island locations where the hydrodynamic conditions are more suitable for plants germination, growth and survival in relation to the river hydrograph statistics. This information is a first step to build a stochastic model able to predict the future evolution and progress of the restoration action of the investigated river reach. We focus at the main island of River Thur at Niederneunforn (Canton Thurgau, Switzerland), the restoration success of which is investigated from a mechanistic viewpoint in the research project "REstored CORridor Dynamics" (www.record.ethz.ch). Accordingly, we analyze two recent Digital Elevation Models (1 year difference), which were first corrected to account for the river bathymetry, and then we compare them in order to extract relevant interannual morphological changes. Using a two dimensional numerical hydrodynamic model we simulate several flow conditions ranging from the minimum recorded flow up to the one that completely inundates the island. Hence, we build inundation maps of the island that we associate to the frequency and the submergence duration of every area. We then correlate such results to the observed survival rate and the root characteristics of a sample of 1-year old transplanted cuttings. Despite limited in number, the investigated sample suggests that roots are shot from different points of the cuttings, which seem to reflect their location on the island and the direction of major resistance to flow erosion, also in agreement with the inundation maps.

Pasquale, N.; Perona, P.; Jiang, Z.; Burlando, P.

2009-04-01

199

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

E-print Network

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

200

More on the elongational viscosity of an oriented fiber assembly  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

201

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

202

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.

203

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

Microsoft Academic Search

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

Theodore C. Hsiao; Liu-Kang Xu

2000-01-01

204

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

PubMed

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

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

2014-03-01

205

Modulation of germination, elongation growth and flowering time in plants  

E-print Network

Modulation of germination, elongation growth and flowering time in plants Reference Number B69259 Background · The present invention relates to a method for modulating plant developmen- tal processes that have direct impact on plant growth and yield. · Identified genes act downstream from the gibberelic

206

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

2013-11-01

207

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

PubMed Central

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

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

2014-01-01

208

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

209

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. PMID:12223628

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

1997-01-01

210

Basipetal propagation of gravity-induced surface pH changes along primary roots of Lepidium sativum L.  

PubMed

While there is ample evidence for a role of auxin in root gravitropism, the seeming rapidity of gravi-induced changes in electrical parameters has so far been an argument against auxin being a primary signal in gravitropic signal transmission. To address this problem, we re-investigated the effect of gravistimulation on membrane voltages of Lepidium sativum L. and Vigna mungo L. root cells. In our hands, gravistimulation did not induce changes in membrane voltage in cells of the root cap statenchyma, root meristem or apical elongation zone that can be correlated with the orientation of the cells relative to the gravity vector. While these results challenge a model of rapid electrically based signal transmission, there is evidence for a slower signal propagation along gravistimulated L. sativum roots. Using multiple proton-selective microelectrodes to simultaneously measure surface pH on opposite root flanks at different distances from the root tip, we observed gravi-induced asymmetric pH changes at the surface of all investigated root zones. Upon gravistimulation, the surface pH decreased on the physically upper root flank and increased on the lower flank. The pH asymmetry appeared first [2.1+/-0.4 min (mean +/- SD) after tilting] at the root cap and then - with incrementing lag times - at the meristem (after 2.5+/-0.3 min at 300 micro m from root tip; after 3.7+/-0.4 min at 700 micro m) and apical elongation zone (4.8+/-0.5 min at 1,000 micro m), suggesting a basipetal progression of differential surface acidification at a rate of 250-350 micro m min(-1), consistent with reported auxin transport rates. PMID:12355158

Monshausen, Gabriele B; Sievers, Andreas

2002-10-01

211

Roots of diversity relations  

Microsoft Academic Search

The species-area relationship is one of the central generalizations in ecology however its origin has remained a puzzle. Since ecosystems are understood as energy transduction systems, the regularities in species richness are considered to result from ubiquitous imperatives in energy transduction. From a thermodynamic point of view, organisms are transduction mechanisms that distribute an influx of energy down along the

Peter Wurtz; Arto Annila

2009-01-01

212

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

Microsoft Academic Search

The rooting capacities of tips of seedling, juvenile and mature shoots of Sequoiadendron giganteum were compared on different rooting media (inductive and expressive media) after passage on an elongating medium. None of the cuttings rooted when continuously kept on medium containing the auxin NAA and vitamin D2. Peroxidase activity of all those cuttings on NAA+D2 first increased during the 7–9

J. Y. Berthon; N. Boyer; Th. Gaspar

1987-01-01

213

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. PMID:21807692

Kato, Yoichiro; Okami, Midori

2011-01-01

214

An endogenous artificial microRNA system for unraveling the function of root endosymbioses related genes in Medicago truncatula  

PubMed Central

Background Legumes have the unique capacity to undergo two important root endosymbioses: the root nodule symbiosis and the arbuscular mycorrhizal symbiosis. Medicago truncatula is widely used to unravel the functions of genes during these root symbioses. Here we describe the development of an artificial microRNA (amiR)-mediated gene silencing system for M. truncatula roots. Results The endogenous microRNA (miR) mtr-miR159b was selected as a backbone molecule for driving amiR expression. Heterologous expression of mtr-miR159b-amiR constructs in tobacco showed that the backbone is functional and mediates an efficient gene silencing. amiR-mediated silencing of a visible marker was also effective after root transformation of M. truncatula constitutively expressing the visible marker. Most importantly, we applied the novel amiR system to shed light on the function of a putative transcription factor, MtErf1, which was strongly induced in arbuscule-containing cells during mycorrhizal symbiosis. MtPt4 promoter driven amiR-silencing led to strongly decreased transcript levels and deformed, non-fully truncated arbuscules indicating that MtErf1 is required for arbuscule development. Conclusions The endogenous amiR system demonstrated here presents a novel and highly efficient tool to unravel gene functions during root endosymbioses. PMID:23679580

2013-01-01

215

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

PubMed

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

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

2013-03-01

216

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

PubMed Central

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

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

2000-01-01

217

Root gravitropism in response to a signal originating outside of the cap  

Microsoft Academic Search

We have developed image analysis software linked to a rotating stage, allowing constraint of any user-selected region of a root at a prescribed angle during root gravitropism. This device allows the cap of a graviresponding root to reach vertical while maintaining a selected region within the elongation zone at a gravistimulated angle. Under these conditions gravitropic curvature of roots of

Chris Wolverton; Jack L. Mullen; Hideo Ishikawa; Michael L. Evans

2002-01-01

218

Anisotropic rigidity sensing on grating topography directs human mesenchymal stem cell elongation.  

PubMed

Through mechanotransduction, cells can sense physical cues from the extracellular environment and convert them into internal signals that affect various cellular functions. For example, human mesenchymal stem cells (hMSCs) cultured on topographical gratings have been shown to elongate and differentiate to different extents depending on grating width. Using a combination of experiments and mathematical modeling, the physical parameters of substrate topography that direct cell elongation were determined. On a variety of topographical gratings with different grating widths, heights and rigidity, elongation of hMSCs was measured and a monotonic increase was observed for grating aspect ratio (crosssectional height to line-width ratio) between 0.035 and 2. The elongation was also dependent on the grating substrate rigidity over a range of 0.18-1.43 MPa. A mathematical model was developed to explain our observations by relating cell elongation to the anisotropic deformation of the gratings and how this anisotropy depends on the aspect ratio and rigidity of the gratings. Our model was in good agreement with the experimental data for the range of grating aspect ratio and substrate rigidity studied. In addition, we also showed that the percentage of aligned cells, which had a strong linear correlation with elongation for slightly elongated cells, saturated toward 100 % at higher level of cell elongation. Our results may be useful in designing gratings to elicit specific cellular responses that may depend on the extent of cell elongation. PMID:23529613

Wong, Sum Thai; Teo, Soo-Kng; Park, Sungsu; Chiam, Keng-Hwee; Yim, Evelyn K F

2014-01-01

219

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

220

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

Microsoft Academic Search

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 µM) that did not affect root

Charles L. Stinemetz; Karl H. Hasenstein; Linda M. Young; Michael L. Evans

1992-01-01

221

Synthesis and Apparent Turnover of Acid Invertase in Relation to Invertase Inhibitor in Wounded Sweet Potato Root Tissue 1  

PubMed Central

Previously we showed that acid invertase activity increased and then decreased rapidly in wounded sweet potato (Ipomoea batatas Liam.) root tissue, and that the tissue contained a heat-stable, proteinaceous inhibitor with a molecular weight of about 19,500 daltons. In response to wounding of sweet potato root tissue, inhibitor activity decreased during the increase in invertase activity but later increased slightly when invertase activity declined. Cycloheximide treatment did not affect the decrease in inhibitor activity that occurred during the early incubation stage, but did inhibit the increase in inhibitor activity that occurred during the late incubation stage. Intrinsic invertase activity, which was assayed after removing the inhibitor, increased and then decreased after wounding, as apparent activity did. The degradative rate of acid invertase in root discs, when assayed by intrinsic activity, was roughly the same during both the early and late incubation stages after wounding, and the degradative rate of the enzyme during the late incubation stage was unaffected by cycloheximide treatment. These results suggest that in sweet potato root discs, enzyme synthesis occurs during the early incubation stage, and ceases during the late incubation stage; however, the enzyme undergoes constant degradation. The change in acid invertase activity after wounding seems to be controlled in root tissue by the interactions of inhibitor-binding and turnover of the enzyme protein. PMID:16659960

Matsushita, Kazunobu; Uritani, Ikuzo

1977-01-01

222

Single-molecule studies of RNAPII elongation.  

PubMed

Elongation, the transcriptional phase in which RNA polymerase (RNAP) moves processively along a DNA template, occurs via a fundamental enzymatic mechanism that is thought to be universally conserved among multi-subunit polymerases in all kingdoms of life. Beyond this basic mechanism, a multitude of processes are integrated into transcript elongation, among them fidelity control, gene regulatory interactions involving elongation factors, RNA splicing or processing factors, and regulatory mechanisms associated with chromatin structure. Many kinetic and molecular details of the mechanism of the nucleotide addition cycle and its regulation, however, remain elusive and generate continued interest and even controversy. Recently, single-molecule approaches have emerged as powerful tools for the study of transcription in eukaryotic organisms. Here, we review recent progress and discuss some of the unresolved questions and ongoing debates, while anticipating future developments in the field. This article is part of a Special Issue entitled: RNA Polymerase II Transcript Elongation. PMID:22982192

Zhou, Jing; Schweikhard, Volker; Block, Steven M

2013-01-01

223

Ion-Accelerator Grids With Elongated Holes  

NASA Technical Reports Server (NTRS)

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

Mueller, Juergen

1996-01-01

224

The establishment of asymmetry in Arabidopsis lateral root founder cells is regulated by LBD16/ASL18 and related LBD/ASL proteins.  

PubMed

In most dicot plants, lateral root (LR) formation, which is important for the construction of the plant root system, is initiated from coordinated asymmetric cell divisions (ACD) of the primed LR founder cells in the xylem pole pericycle (XPP) of the existing roots. In Arabidopsis thaliana, two AUXIN RESPONSE FACTORs (ARFs), ARF7 and ARF19, positively regulate LR formation through activation of the plant-specific transcriptional regulators LATERAL ORGAN BOUNDARIES-DOMAIN 16/ASYMMETRIC LEAVES2-LIKE 18 (LBD16/ASL18) and the other related LBD/ASL genes. The exact biological role of these LBD/ASLs in LR formation is still unknown. Here, we demonstrate that LBD16/ASL18 is specifically expressed in the LR founder cells adjacent to the XPP before the first ACD and that it functions redundantly with the other auxin-inducible LBD/ASLs in LR initiation. The spatiotemporal expression of LBD16/ASL18 during LR initiation is dependent on the SOLITARY-ROOT (SLR)/IAA14-ARF7-ARF19 auxin signaling module. In addition, XPP-specific expression of LBD16/ASL18 in arf7 arf19 induced cell divisions at XPP, thereby restoring the LR phenotype. We also demonstrate that expression of LBD16-SRDX, a dominant repressor of LBD16/ASL18 and its related LBD/ASLs, does not interfere in the specification of LR founder cells with local activation of the auxin response, but it blocks the polar nuclear migration in LR founder cells before ACD, thereby blocking the subsequent LR initiation. Taken together, these results indicate that the localized activity of LBD16/ASL18 and its related LBD/ASLs is involved in the symmetry breaking of LR founder cells for LR initiation, a key step for constructing the plant root system. PMID:22278921

Goh, Tatsuaki; Joi, Shunpei; Mimura, Tetsuro; Fukaki, Hidehiro

2012-03-01

225

Correlations between polyamine ratios and growth patterns in seedling roots  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

226

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

PubMed

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

Nair, Prakash M Gopalakrishnan; Chung, Ill Min

2014-11-01

227

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

PubMed Central

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 (Lpr) and NaCl permeability (Psr) 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

2011-01-01

228

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

229

Venus - A Large Elongated Caldera 'Sacajawea Patera  

NASA Technical Reports Server (NTRS)

This Magellan image reveals Sacajawea Patera, a large, elongate caldera located in Western Ishtar Terra on the smooth plateau of Lakshmi Planum. The image is centered at 64.5 degrees North latitude and 337 degrees East longitude. It is approximately 420 kilometers (252 miles) wide at the base. Sacajawea is a depression approximately 1-2 kilometers (0.6-1.2 miles) deep and 120 x 215 kilometers (74 x 133 miles) in diameter; it is elongate in a southwest-northeast direction. The depression is bounded by a zone of circumferential curvilinear structures interpreted to be graben and fault scarps. These structures are spaced 0.5-4 kilometers (0.3-2.5 miles) apart, are 0.6-4.0 kilometers (0.4-2.5 miles) in width and up to 100 kilometers (62 miles) in length. Extending up to approximately 140 kilometers (87 miles) in length from the southeast of the patera is a system of linear structures thought to represent a flanking rift zone along which the lateral injection and eruption of magma may have occurred. A shield edifice 12 kilometers (7 miles) in diameter with a prominent central pit lies along the trend of one of these features. The impact crater Zlata, approximately 6 kilometers (4 miles) in diameter is located within the zone of graben to the northwest of the patera. Few flow features are observed in association with Sacajawea, possibly due to age and state of degradation of the flows. Mottled bright deposits 4-20 kilometers (2.5-12 miles) in width are located near the periphery and in the center of the patera floor within local topographic lows. Diffuse patches of dark material approximately 40 kilometers (25 miles) in width are observed southwest of the patera, superposed on portions of the surrounding graben. The formation of Sacajawea is thought to be related to the drainage and collapse of a large magma chamber. Gravitational relaxation may have caused the resultant caldera to sag, producing the numerous faults and graben that circumscribe the patera. Regions of complex, highly deformed tessera-like terrain are located north and east of the patera and are seen in the upper portion of the image.

1991-01-01

230

Expression of sulfur uptake assimilation-related genes in response to cadmium, bensulfuron-methyl and their co-contamination in rice roots.  

PubMed

The responses of sulfur (S) uptake assimilation-related genes' expression in roots of two rice cultivars to cadmium (Cd), bensulfuron-methyl (BSM) and their co-contamination (Cd+BSM) were investigated by gene-chip microarray analysis and quantitative real-time PCR (QRT-PCR) technology. Treatments of Cd and Cd+BSM induced expression of sulfate transporter and permease genes, and promoted sulfate uptake in rice roots. Cd+BSM could alleviate Cd toxicity to cv. Fengmeizhan seedlings, probably due to Cd+BSM promoting greater S absorption by seedlings. Cd and Cd+BSM induced expression of sulfate assimilation-related genes, and thus activated the sulfur assimilation pathway. Cd and Cd+BSM induced expression of phytochelatin synthase and metallothionein genes, and induced expression of glutathione S-transferases (GSTs), glutathione synthase (GS) and S-containing antioxidation enzyme genes, which detoxified Cd(2+). It is suggested that (to cope with the toxicity of Cd, BSM and their co-contamination) the S uptake and assimilation pathway was activated in rice roots by increased expression of related genes, thus enhancing the supply of organic S for synthesis of Cd or BSM resistance-related substances. PMID:25079279

Zhou, Jian; Wang, Zegang; Huang, Zhiwei; Lu, Chao; Han, Zhuo; Zhang, Jianfeng; Jiang, Huimin; Ge, Cailin; Yang, Juncheng

2014-03-01

231

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

PubMed Central

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

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

2013-01-01

232

Differential response of Arabidopsis leaves and roots to cadmium: glutathione-related chelating capacity vs antioxidant capacity.  

PubMed

This study aims to uncover the spatiotemporal involvement of glutathione (GSH) in two major mechanisms of cadmium (Cd)-induced detoxification (i.e. chelation and antioxidative defence). A kinetic study was conducted on hydroponically grown Arabidopsis thaliana (L. Heyhn) to gain insight into the early events after exposure to Cd. Cadmium detoxification was investigated at different levels, including gene transcripts, enzyme activities and metabolite content. Data indicate a time-dependent response both within roots and between plant organs. Early on in roots, GSH was preferentially allocated to phytochelatin (PC) synthesis destined for Cd chelation. This led to decreased GSH levels, without alternative pathways activated to complement GSH's antioxidative functions. After one day however, multiple antioxidative pathways increased including superoxide dismutase (SOD), ascorbate (AsA) and catalase (CAT) to ensure efficient neutralization of Cd-induced reactive oxygen species (ROS). As a consequence of Cd retention and detoxification in roots, a delayed response occurred in leaves. Together with high leaf thiol contents and possibly signalling responses from the roots, the leaves were protected, allowing them sufficient time to activate their defence mechanisms. PMID:25049163

Jozefczak, Marijke; Keunen, Els; Schat, Henk; Bliek, Mattijs; Hernández, Luis E; Carleer, Robert; Remans, Tony; Bohler, Sacha; Vangronsveld, Jaco; Cuypers, Ann

2014-10-01

233

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

Microsoft Academic Search

Summary We measured respiration of 20-year-old Pinus radiata D. Don trees growing in control (C), irrigated (I), and irrigated + fertilized (IL) stands in the Biology of Forest Growth experimental plantation near Canberra, Australia. Res- piration was measured on fully expanded foliage, live branches, boles, and fine and coarse roots to determine the relationship between CO2 efflux, tissue temperature, and

MICHAEL G. RYAN; ROBERT M. HUBBARD; SILVIA PONGRACIC; R. J. RAISON; ROSS E. MCMURTRIE

234

Growth promotion-related miRNAs in Oncidium orchid roots colonized by the endophytic fungus Piriformospora indica.  

PubMed

Piriformospora indica, an endophytic fungus of Sebacinales, colonizes the roots of a wide range of host plants and establishes various benefits for the plants. In this work, we describe miRNAs which are upregulated in Oncidium orchid roots after colonization by the fungus. Growth promotion and vigorous root development were observed in Oncidium hybrid orchid, while seedlings were colonized by P. indica. We performed a genome-wide expression profiling of small RNAs in Oncidium orchid roots either colonized or not-colonized by P. indica. After sequencing, 24,570,250 and 24744,141 clean reads were obtained from two libraries. 13,736 from 17,036,953 unique sequences showed homology to either 86 miRNA families described in 41 plant species, or to 46 potential novel miRNAs, or to 51 corresponding miRNA precursors. The predicted target genes of these miRNAs are mainly involved in auxin signal perception and transduction, transcription, development and plant defense. The expression analysis of miRNAs and target genes demonstrated the regulatory functions they may participate in. This study revealed that growth stimulation of the Oncidium orchid after colonization by P. indica includes an intricate network of miRNAs and their targets. The symbiotic function of P. indica on Oncidium orchid resembles previous findings on Chinese cabbage. This is the first study on growth regulation and development of Oncidium orchid by miRNAs induced by the symbiotic fungus P. indica. PMID:24409313

Ye, Wei; Shen, Chin-Hui; Lin, Yuling; Chen, Peng-Jen; Xu, Xuming; Oelmüller, Ralf; Yeh, Kai-Wun; Lai, Zhongxiong

2014-01-01

235

Growth Promotion-Related miRNAs in Oncidium Orchid Roots Colonized by the Endophytic Fungus Piriformospora indica  

PubMed Central

Piriformospora indica, an endophytic fungus of Sebacinales, colonizes the roots of a wide range of host plants and establishes various benefits for the plants. In this work, we describe miRNAs which are upregulated in Oncidium orchid roots after colonization by the fungus. Growth promotion and vigorous root development were observed in Oncidium hybrid orchid, while seedlings were colonized by P. indica. We performed a genome-wide expression profiling of small RNAs in Oncidium orchid roots either colonized or not-colonized by P. indica. After sequencing, 24,570,250 and 24744,141 clean reads were obtained from two libraries. 13,736 from 17,036,953 unique sequences showed homology to either 86 miRNA families described in 41 plant species, or to 46 potential novel miRNAs, or to 51 corresponding miRNA precursors. The predicted target genes of these miRNAs are mainly involved in auxin signal perception and transduction, transcription, development and plant defense. The expression analysis of miRNAs and target genes demonstrated the regulatory functions they may participate in. This study revealed that growth stimulation of the Oncidium orchid after colonization by P. indica includes an intricate network of miRNAs and their targets. The symbiotic function of P. indica on Oncidium orchid resembles previous findings on Chinese cabbage. This is the first study on growth regulation and development of Oncidium orchid by miRNAs induced by the symbiotic fungus P. indica. PMID:24409313

Lin, Yuling; Chen, Peng-Jen; Xu, Xuming; Oelmuller, Ralf; Yeh, Kai-Wun; Lai, Zhongxiong

2014-01-01

236

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. PMID:12223650

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

1997-01-01

237

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

EPA Science Inventory

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

238

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

239

Nerve growth factor stimulates synthesis of calcitonin gene-related peptide in dorsal root ganglion cells during sensory regeneration in capsaicin-treated rats  

Microsoft Academic Search

Administration of human recombinant nerve growth factor (rhNGF) into one hindpaw of capsaicin-treated rats can locally facilitate the regeneration of calcitonin gene-related peptide (CGRP)-containing primary sensory neurons (Schicho, R., Skofitsch, G., Donnerer, J., 1999. Brain Res. 815, 60–69). In this study we used in situ hybridization histochemistry (ISH) to determine synthesis of CGRP mRNA in lumbar L4 dorsal root ganglion

Rudolf Schicho; Josef Donnerer

1999-01-01

240

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

PubMed Central

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

2013-01-01

241

Comparison of Genomes of Brucella melitensis M28 and the B. melitensis M5-90 Derivative Vaccine Strain Highlights the Translation Elongation Factor Tu Gene tuf2 as an Attenuation-Related Gene  

PubMed Central

Brucella melitensis causes brucellosis, a disease affecting sheep, cattle, and sometimes humans. Attenuated B. melitensis strain M5-90, derived from virulent strain M28, is widely used as a live vaccine in ruminants in China. Genetic differences between the strains may cast light on the mechanism of attenuation. We recently reported the complete genomic sequences of M28 and M5-90. Genome organization is highly conserved between these isolates, and also with virulent strains 16 M and ATCC 23457. Analysis revealed 23 open reading frames (ORFs) with consistent differences between M5-90 and the virulent strains. Notably, the tuf2 gene encoding translation elongation factor EF-Tu from M5-90 contained 50 single nucleotide polymorphisms (SNPs) and 9 gaps (indels) compared to tuf2 of M28 or of the other virulent strains. There were no changes in tuf1. To evaluate the potential role of EF-Tu in pathogenesis, tuf1 and tuf2 mutants of M28 and an M5-90 strain harboring wild-type tuf2 were constructed, and their virulence/attenuation was evaluated in vivo. We report that the tuf2 gene plays an important role in the attenuation of M5-90 virulence. PMID:23716607

Wang, Fangkun; Qiao, Zujian; Hu, Sen; Liu, Wenxing; Zheng, Huajun; Liu, Sidang; Zhao, Xiaomin

2013-01-01

242

Chitinase-Like Protein CTL1 Plays a Role in Altering Root System Architecture in Response to Multiple Environmental Conditions1[C][W][OA  

PubMed Central

Plant root architecture is highly responsive to changes in nutrient availability. However, the molecular mechanisms governing the adaptability of root systems to changing environmental conditions is poorly understood. A screen for abnormal root architecture responses to high nitrate in the growth medium was carried out for a population of ethyl methanesulfonate-mutagenized Arabidopsis (Arabidopsis thaliana). The growth and root architecture of the arm (for anion altered root morphology) mutant described here was similar to wild-type plants when grown on low to moderate nitrate concentrations, but on high nitrate, arm exhibited reduced primary root elongation, radial swelling, increased numbers of lateral roots, and increased root hair density when compared to the wild-type control. High concentrations of chloride and sucrose induced the same phenotype. In contrast, hypocotyl elongation in the dark was decreased independently of nitrate availability. Positional cloning identified a point mutation in the AtCTL1 gene that encodes a chitinase-related protein, although molecular and biochemical analysis showed that this protein does not possess chitinase enzymatic activity. CTL1 appears to play two roles in plant growth and development based on the constitutive effect of the arm mutation on primary root growth and its conditional impact on root architecture. We hypothesize that CTL1 plays a role in determining cell wall rigidity and that the activity is differentially regulated by pathways that are triggered by environmental conditions. Moreover, we show that mutants of some subunits of the cellulose synthase complex phenocopy the conditional effect on root architecture under nonpermissive conditions, suggesting they are also differentially regulated in response to a changing environment. PMID:20007445

Hermans, Christian; Porco, Silvana; Verbruggen, Nathalie; Bush, Daniel R.

2010-01-01

243

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

244

Anatomical responses of root tips to boron deficiency II. Effect of boron deficiency on the cellular growth and development in root tips  

Microsoft Academic Search

Changes induced in the tissue structure and the cellular patterns of young tomato root tips by the absence of boron in the nutrient solution were investigated.Boron deficiency caused primarily the inhibition of cell division and cell elongation in root apices, and the cells of boron-deficient root tips were fully vacuolated. The cell wall in the apical region was thickened by

Hiroshi Kouchi; Kikuo Kumazawa

1975-01-01

245

Influence of nursery soil amendments on water relations, root architectural development, and field performance of Douglas-fir transplants  

Microsoft Academic Search

This experiment evaluated the influence of manure, peat, and vermiculite incorporated at low and high rates (0.0118 and 0.0236 m3\\/m2) and under two soil moisture regimes on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedling (1+0 for 1+1) xylem water potential (?xylem), whole-plant growth, root architectural development, and subsequent field performance under fertilized and non-fertilized conditions. Trends in soil moisture retention were

Douglass F. Jacobs; Robin Rose; Diane L. Haase; Paul D. Morgan

2003-01-01

246

Single-molecule studies of RNAPII elongation  

PubMed Central

Elongation, the transcriptional phase in which RNA polymerase (RNAP) moves processively along a DNA template, occurs via a fundamental enzymatic mechanism that is thought to be universally conserved among multi-subunit polymerases in all kingdoms of life. Beyond this basic mechanism, a multitude of processes are integrated into transcript elongation, among them fidelity control, gene regulatory interactions involving elongation factors, RNA splicing or processing factors, and regulatory mechanisms associated with chromatin structure. Many kinetic and molecular details of the mechanism of the nucleotide addition cycle and its regulation, however, remain elusive and generate continued interest and even controversy. Recently, single-molecule approaches have emerged as powerful tools for the study of transcription in eukaryotic organisms. Here, we review recent progress and discuss some of the unresolved questions and ongoing debates, while anticipating future developments in the field. PMID:22982192

Zhou, Jing; Schweikhard, Volker; Block, Steven M.

2012-01-01

247

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

PubMed Central

Cd from roots of maize was partitioned in seedlings exposed to 3 microM CdSO4 for 1 to 7 d. Most of the root Cd (92-94%) was buffer soluble and provided the classical metal-induced cysteine-rich, high-molecular-weight Cd-binding complex. This complex, however, bound only part of the Cd within the roots, from 19% after 1 d of exposure to 59% by d 7. Three families of peptides formed the Cd-binding complex: (gamma-glutamic acid-cysteine)n-glycine [(gamma-Glu-Cys)n-Gly], or phytochelatins, (gamma-Glu-Cys)n, and (gamma-Glu-Cys)n-Glu. The monothiols gamma-Glu-Cys-Gly (glutathione), gamma-Glu-Cys, and gamma-Glu-Cys-Glu were absent from the complex. The n2 oligomers of any peptide were the least concentrated, whereas the n3 and n4 oligomers increased in the complex with exposure to Cd. By d 7, 75% of (gamma-Glu-Cys)4-Gly, 80% of (gamma-Glu-Cys)4, and 73% of (gamma-Glu-Cys)3-Glu were complexed with Cd. The peptide thiol:Cd molar ratio for the complexes was 1.01 +/- 0.07, as if the minimal amount of thiol was used to bind Cd. Acid-labile sulfide occurred in the complexes from d 1 onward at the low S2-;Cd molar ratio of 0.18 +/- 0.02. PMID:7480321

Rauser, W E; Meuwly, P

1995-01-01

248

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

PubMed

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

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

2014-06-01

249

New Insights on Plant Cell Elongation: A Role for Acetylcholine  

PubMed Central

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

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

2014-01-01

250

Inhibition of Eukaryotic Translation Elongation by Cycloheximide and Lactimidomycin  

PubMed Central

Although the protein synthesis inhibitor cycloheximide (CHX) has been known for decades, its precise mechanism of action remains incompletely understood. The glutarimide portion of CHX is seen in a family of structurally related natural products including migrastatin, isomigrastatin and lactimidomycin (LTM). LTM, isomigrastatin and analogs were found to have a potent antiproliferative effect on tumor cell lines and selectively inhibit protein translation. A systematic comparative study of the effects of CHX and LTM on protein translation revealed both similarities and differences between the two inhibitors. Both LTM and CHX were found to block the translocation step in elongation. Footprinting experiments revealed protection of a single cytidine nucleotide (C3993) in the E-site of the 60S ribosomal subunit, defining a common binding pocket for both inhibitors in the ribosome. These results shed new light on the molecular mechanism of inhibition of translation elongation by both CHX and LTM. PMID:20118940

Schneider-Poetsch, Tilman; Ju, Jianhua; Eyler, Daniel E; Dang, Yongjun; Bhat, Shridhar; Merrick, William C; Green, Rachel; Shen, Ben; Liu, Jun O

2010-01-01

251

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. PMID:19704705

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

2009-01-01

252

Gravitropism of Arabidopsis thaliana Roots Requires the Polarization of PIN2 toward the Root Tip in Meristematic  

E-print Network

Gravitropism of Arabidopsis thaliana Roots Requires the Polarization of PIN2 toward the Root Tip to the elongation zone, referred to here as shootward, governs gravitropic bending. Shootward polar auxin transport, and hence gravitropism, depends on the polar deployment of the PIN-FORMED auxin efflux carrier PIN2

Baskin, Tobias

253

Neuroprotective Copper Bis(thiosemicarbazonato) Complexes Promote Neurite Elongation  

PubMed Central

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

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

2014-01-01

254

Neuroprotective copper bis(thiosemicarbazonato) complexes promote neurite elongation.  

PubMed

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

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

2014-01-01

255

Intracellular trafficking and proteolysis of the Arabidopsis auxin-efflux facilitator PIN2 are involved in root gravitropism  

Microsoft Academic Search

Root gravitropism describes the orientation of root growth along the gravity vector and is mediated by differential cell elongation in the root meristem. This response requires the coordinated, asymmetric distribution of the phytohormone auxin within the root meristem, and depends on the concerted activities of PIN proteins and AUX1 — members of the auxin transport pathway. Here, we show that

Lindy Abas; René Benjamins; Nenad Malenica; Tomasz Paciorek; Justyna Wišniewska; Tobias Sieberer; Ji?í Friml; Christian Luschnig

2006-01-01

256

Reorientation of elongated particles at density interfaces  

NASA Astrophysics Data System (ADS)

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

Doostmohammadi, A.; Ardekani, A. M.

2014-09-01

257

Rhizome elongation and seagrass clonal growth  

Microsoft Academic Search

A compilation of published and original data on rhizome morphometry, horizontal and vertical elongation rates and branching patterns for 27 seagrass species developing in 192 seagrass stands allowed an examination of the variability of seagrass rhizome and clonal growth programmes across and within species. Seagrass horizontal rhizomes extend at rates ranging between 1.2 and 574 cm yr(-1), develop a branch,

N. Marbà; C. M. Duarte

1998-01-01

258

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

PubMed Central

With the aid of an extracellular vibrating electrode, natural electric fields were detected and measured in the medium near growing roots and root hairs of barley seedlings. An exploration of these fields indicates that both the root as a whole, as well as individual root hairs, drive large steady currents through themselves. Current consistently enters both the main elongation zone of the root as well as the growing tips of elongating root hairs; it leaves the surface of the root beneath the root hairs. These currents enter with a density of about 2 microamperes per square centimeter, leave with a density of about 0.5 to 1 microampere per square centimeter, and total about 30 nanoamperes. Responses of the natural fields to changes in the ionic composition of the medium as well as observations of the pH pattern in the medium near the roots (made with bromocresol purple) together indicate that much of the current consists of hydrogen ions. Altogether, H+ ions seem to leak into growing cells or cell parts and to be pumped out of nongrowing ones. Images PMID:16661000

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

1979-01-01

259

Role of cytokinin in the regulation of root gravitropism.  

PubMed

The models explaining root gravitropism propose that the growth response of plants to gravity is regulated by asymmetric distribution of auxin (indole-3-acetic acid, IAA). Since cytokinin has a negative regulatory role in root growth, we suspected that it might function as an inhibitor of tropic root elongation during gravity response. Therefore, we examined the free-bioactive-cytokinin-dependent ARR5::GUS expression pattern in root tips of transformants of Arabidopsis thaliana (L.) Heynh., visualized high cytokinin concentrations in the root cap with specific monoclonal antibodies, and complemented the analyses by external application of cytokinin. Our findings show that mainly the statocytes of the cap produce cytokinin, which may contribute to the regulation of root gravitropism. The homogenous symmetric expression of the cytokinin-responsive promoter in vertical root caps rapidly changed within less than 30 min of gravistimulation into an asymmetrical activation pattern, visualized as a lateral, distinctly stained, concentrated spot on the new lower root side of the cap cells. This asymmetric cytokinin distribution obviously caused initiation of a downward curvature near the root apex during the early rapid phase of gravity response, by inhibiting elongation at the lower side and promoting growth at the upper side of the distal elongation zone closely behind the root cap. Exogenous cytokinin applied to vertical roots induced root bending towards the application site, confirming the suspected inhibitory effect of cytokinin in root gravitropism. Our results suggest that the early root graviresponse is controlled by cytokinin. We conclude that both cytokinin and auxin are key hormones that regulate root gravitropism. PMID:15365840

Aloni, Roni; Langhans, Markus; Aloni, Erez; Ullrich, Cornelia I

2004-11-01

260

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

PubMed

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. PMID:8655563

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

1996-06-01

261

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. PMID:8655563

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

1996-01-01

262

Plant growth-promoting bacteria and nitrate availability: impacts on root development and nitrate uptake  

Microsoft Academic Search

Plant growth-promoting bacteria (PGPB) and NO - 3 availability both affect NO - 3 uptake and root architec- ture. The presence of external NO - 3 induces the expression of NO - 3 transporter genes and elicits lat- eral root elongation in the part of the root system exposed to the NO - 3 supply. By contrast, an increase in

Sophie Mantelin; Bruno Touraine

2003-01-01

263

The multiple contributions of phytochromes to the control of internode elongation in rice.  

PubMed

Although phyAphyBphyC phytochrome-null mutants in rice (Oryza sativa) have morphological changes and exhibit internode elongation, even as seedlings, it is unknown how phytochromes contribute to the control of internode elongation. A gene for 1-aminocyclopropane-1-carboxylate oxidase (ACO1), which is an ethylene biosynthesis gene contributing to internode elongation, was up-regulated in phyAphyBphyC seedlings. ACO1 expression was controlled mainly by phyA and phyB, and a histochemical analysis showed that ACO1 expression was localized to the basal parts of leaf sheaths of phyAphyBphyC seedlings, similar to mature wild-type plants at the heading stage, when internode elongation was greatly promoted. In addition, the transcription levels of several ethylene- or gibberellin (GA)-related genes were changed in phyAphyBphyC mutants, and measurement of the plant hormone levels indicated low ethylene production and bioactive GA levels in the phyAphyBphyC mutants. We demonstrate that ethylene induced internode elongation and ACO1 expression in phyAphyBphyC seedlings but not in the wild type and that the presence of bioactive GAs was necessary for these effects. These findings indicate that phytochromes contribute to multiple steps in the control of internode elongation, such as the expression of the GA biosynthesis gene OsGA3ox2, ACO1 expression, and the onset of internode elongation. PMID:21911595

Iwamoto, Masao; Kiyota, Seiichiro; Hanada, Atsushi; Yamaguchi, Shinjiro; Takano, Makoto

2011-11-01

264

Parameterizing complex root water uptake models - the arrangement of root hydraulic properties within the root architecture affects dynamics and efficiency of root water uptake  

NASA Astrophysics Data System (ADS)

Detailed three-dimensional models of root water uptake have become increasingly popular for investigating the process of root water uptake. However they suffer from a lack of information in important parameters, especially distribution of root hydraulic properties. In this paper we explore the role that arrangement of root hydraulic properties and root system topology play for modelled uptake dynamics. We apply microscopic models of single root structures to investigate the mechanisms shaping uptake dynamics and demonstrate the effects in a complex three dimensional root water uptake model. We introduce two efficiency indices, for (a) overall plant resistance and (b) water stress and show that an appropriate arrangement of root hydraulic properties can increase modelled efficiency of root water uptake in single roots, branched roots and entire root systems. The average uptake depth of the complete root system was not influenced by parameterization. However, other factors such as evolution of collar potential, which is related to the plant resistance, root bleeding and redistribution patterns were strongly affected by the parameterization. Root systems are more efficient when they are assembled of different root types, allowing for separation of root function in uptake (short young) roots and transport (longer mature) roots. Results become similar, as soon as this composition is accounted for to some degree (between 40 and 80% of young uptake roots). Overall resistance to root water uptake was decreased up to 40% and total transpiration was increased up to 25% in these composed root systems, compared to homogenous root systems. Also, one parameterization (homogenous young root system) was characterized by excessive bleeding (hydraulic lift), which was accompanied by lowest efficiency. We conclude that heterogeneity of root hydraulic properties is a critical component of complex three dimensional uptake models. Efficiency measures together with information on critical xylem potentials may be useful in parameterizing root property distribution.

Bechmann, M.; Schneider, C.; Carminati, A.; Vetterlein, D.; Attinger, S.; Hildebrandt, A.

2014-01-01

265

Higher order Arabidopsis 14-3-3 mutants show 14-3-3 involvement in primary root growth both under control and abiotic stress conditions.  

PubMed

Arabidopsis 14-3-3 proteins are a family of conserved proteins that interact with numerous partner proteins in a phospho-specific manner, and can affect the target proteins in a number of ways; e.g. modification of enzymatic activity. We isolated T-DNA insertion lines in six 14-3-3 genes within the non-epsilon group that phylogenetically group in three closely related gene pairs. In total, 6 single, 3 double, 12 triple, and 3 quadruple mutants were generated. The mutants were phenotyped for primary root growth on control plates: single and double mutants were indistinguishable from WT, whereas six triples and all quadruples showed a shorter primary root. In addition, length of the first epidermal cell with a visible root hair bulge (LEH) was used to determine primary root elongation on medium containing mannitol and 1-aminocyclopropane-1-carboxylic acid (ACC). This analysis showed clear differences depending on the stress and 14-3-3 gene combinations. Next to the phenotypic growth analyses, a 14-3-3 pull-down assay on roots treated with and without mannitol showed that mannitol stress strongly affects the 14-3-3 interactome. In conclusion, we show gene specificity and functional redundancy among 14-3-3 proteins in primary root elongation under control and under abiotic stress conditions and changes in the 14-3-3 interactome during the onset of stress adaptation. PMID:25189593

van Kleeff, P J M; Jaspert, N; Li, K W; Rauch, S; Oecking, C; de Boer, A H

2014-11-01

266

Higher order Arabidopsis 14-3-3 mutants show 14-3-3 involvement in primary root growth both under control and abiotic stress conditions  

PubMed Central

Arabidopsis 14-3-3 proteins are a family of conserved proteins that interact with numerous partner proteins in a phospho-specific manner, and can affect the target proteins in a number of ways; e.g. modification of enzymatic activity. We isolated T-DNA insertion lines in six 14-3-3 genes within the non-epsilon group that phylogenetically group in three closely related gene pairs. In total, 6 single, 3 double, 12 triple, and 3 quadruple mutants were generated. The mutants were phenotyped for primary root growth on control plates: single and double mutants were indistinguishable from WT, whereas six triples and all quadruples showed a shorter primary root. In addition, length of the first epidermal cell with a visible root hair bulge (LEH) was used to determine primary root elongation on medium containing mannitol and 1-aminocyclopropane-1-carboxylic acid (ACC). This analysis showed clear differences depending on the stress and 14-3-3 gene combinations. Next to the phenotypic growth analyses, a 14-3-3 pull-down assay on roots treated with and without mannitol showed that mannitol stress strongly affects the 14-3-3 interactome. In conclusion, we show gene specificity and functional redundancy among 14-3-3 proteins in primary root elongation under control and under abiotic stress conditions and changes in the 14-3-3 interactome during the onset of stress adaptation. PMID:25189593

van Kleeff, P. J. M.; Jaspert, N.; Li, K. W.; Rauch, S.; Oecking, C.; de Boer, A. H.

2014-01-01

267

Identification of a developmentally regulated translation elongation factor-2 in Tetrahymena thermophila  

Microsoft Academic Search

Protein synthesis occurs in all living organisms and regulation of this process frequently occurs at the level of initiation. In contrast, only a few examples of alterations in elongation are known and these typically involve reversible modification of eEF2. We have identified a gene family in Tetrahymena thermophila that encodes a developmentally regulated eEF2 called EFR (elongation factor-2 related). The

Tania Margarita Malave

2002-01-01

268

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

NASA Technical Reports Server (NTRS)

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

Sullivan, Roy M.; Ghosn, Louis J.

2008-01-01

269

Positional effect of cell inactivation on root gravitropism using heavy-ion microbeams.  

PubMed

When primary root apical tissues of Arabidopsis thaliana were irradiated by heavy-ion microbeams with 120 microm diameter, strong inhibition of root elongation and curvature were observed at the root tip. Irradiation of the cells that become the lower part of the root cap after gravistimulation showed strong inhibition of root curvature, whereas irradiation of the cells that become the upper part of the root cap after gravistimulation did not show severe damage in either root curvature or root growth. Further analysis using smaller area microbeams with 40 microm diameter indicated that the greatest inhibition of curvature occurred at the root tip and the next greatest inhibition occurred in the cells in the lower part of the root cap. These results indicate not only that the root tip and columella cells are the most sensitive sites for root gravity, but also that signalling of root gravity would go through the lower part of the cap cells after perception. PMID:11886888

Tanaka, Atsushi; Kobayashi, Yasuhiko; Hase, Yoshihiro; Watanabe, Hiroshi

2002-04-01

270

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

PubMed

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

Thompson, Matthew V; Holbrook, N Michele

2004-07-01

271

Long-term control of root growth  

DOEpatents

A method and system for long-term control of root growth without killing the plants bearing those roots involves incorporating a 2,6-dinitroaniline in a polymer and disposing the polymer in an area in which root control is desired. This results in controlled release of the substituted aniline herbicide over a period of many years. Herbicides of this class have the property of preventing root elongation without translocating into other parts of the plant. The herbicide may be encapsulated in the polymer or mixed with it. The polymer-herbicide mixture may be formed into pellets, sheets, pipe gaskets, pipes for carrying water, or various other forms. The invention may be applied to other protection of buried hazardous wastes, protection of underground pipes, prevention of root intrusion beneath slabs, the dwarfing of trees or shrubs and other applications. The preferred herbicide is 4-difluoromethyl-N,N-dipropyl-2,6-dinitro-aniline, commonly known as trifluralin.

Burton, Frederick G. (West Richland, WA); Cataldo, Dominic A. (Kennewick, WA); Cline, John F. (Prosser, WA); Skiens, W. Eugene (Richland, WA)

1992-05-26

272

Long-term control of root growth  

SciTech Connect

A method and system for long-term control of root growth without killing the plants bearing those roots involves incorporating a 2,6-dinitroaniline in a polymer and disposing the polymer in an area in which root control is desired. This results in controlled release of the substituted aniline herbicide over a period of many years. Herbicides of this class have the property of preventing root elongation without translocating into other parts of the plant. The herbicide may be encapsulated in the polymer or mixed with it. The polymer-herbicide mixture may be formed into pellets, sheets, pipe gaskets, pipes for carrying water, or various other forms. The invention may be applied to other protection of buried hazardous wastes, protection of underground pipes, prevention of root intrusion beneath slabs, the dwarfing of trees or shrubs and other applications. The preferred herbicide is 4-difluoromethyl-N,N-dipropyl-2,6-dinitro-aniline, commonly known as trifluralin. 7 figs.

Burton, F.G.; Cataldo, D.A.; Cline, J.F.; Skiens, W.E.

1992-05-26

273

Altering Chemosensitivity by Modulating Translation Elongation  

PubMed Central

Background The process of translation occurs at a nexus point downstream of a number of signal pathways and developmental processes. Modeling activation of the PTEN/AKT/mTOR pathway in the E?-Myc mouse is a valuable tool to study tumor genotype/chemosensitivity relationships in vivo. In this model, blocking translation initiation with silvestrol, an inhibitor of the ribosome recruitment step has been showed to modulate the sensitivity of the tumors to the effect of standard chemotherapy. However, inhibitors of translation elongation have been tested as potential anti-cancer therapeutic agents in vitro, but have not been extensively tested in genetically well-defined mouse tumor models or for potential synergy with standard of care agents. Methodology/Principal Findings Here, we chose four structurally different chemical inhibitors of translation elongation: homoharringtonine, bruceantin, didemnin B and cycloheximide, and tested their ability to alter the chemoresistance of E?-myc lymphomas harbouring lesions in Pten, Tsc2, Bcl-2, or eIF4E. We show that in some genetic settings, translation elongation inhibitors are able to synergize with doxorubicin by reinstating an apoptotic program in tumor cells. We attribute this effect to a reduction in levels of pro-oncogenic or pro-survival proteins having short half-lives, like Mcl-1, cyclin D1 or c-Myc. Using lymphomas cells grown ex vivo we reproduced the synergy observed in mice between chemotherapy and elongation inhibition and show that this is reversed by blocking protein degradation with a proteasome inhibitor. Conclusion/Significance Our results indicate that depleting short-lived pro-survival factors by inhibiting their synthesis could achieve a therapeutic response in tumors harboring PTEN/AKT/mTOR pathway mutations. PMID:19412536

Robert, Francis; Carrier, Marilyn; Rawe, Svea; Chen, Samuel; Lowe, Scott; Pelletier, Jerry

2009-01-01

274

Root hydrotropism: an update.  

PubMed

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

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

2013-01-01

275

Elongational viscosity of photo-oxidated LDPE  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

276

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

PubMed

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

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

2014-06-01

277

Numerical Analysis of High-beta Spherical Tokamaks with Varied Elongation  

NASA Astrophysics Data System (ADS)

The effect of plasma elongation on the second-stable spherical tokamak (ST)was numerically studied using the experimentally measuredpressure and current profiles of ultra-high beta STs. The maximum beta of ST over 50% was obtained in the TS-3 ST/CT experimentby applying an external toroidal field to an FRC. It was found that the marginal beta for the ballooning instabilityincreased with the plasma elongation ? of ST. The elongated STs with ? > 2 have the magnetic shear (S) -- pressure gradient(?) profiles located in the second-stable regime for the ballooning mode andthe stability margin increased with ?. The close relation between the absolute minimum-B profile andthe second stability was documented. The effect of elongation on maximum beta was observed to saturatewhen ? exceeded 3, indicating that the optimized elongationfor high-beta STs are located around 2 < ? < 3.

Ogawa, Toru; Kimura, Toshiro; Ono, Yasushi

278

Oxytocin-Induced Activation of Eukaryotic Elongation Factor 2 in Myometrial Cells Is Mediated by Protein Kinase C  

Microsoft Academic Search

The nonapeptide oxytocin (OT) mediates a wide spectrum of biological action, many of them related to reproduction. Re- cently, we have shown that OT exerts a trophic effect on uter- ine smooth muscle cells and induces dephosphorylation, and thus activation, of the translation elongation factor eukary- otic elongation factor 2 (eEF2). The present study was de- signed to elucidate the

Dominic Devost; Marie-Eve Carrier; Hans H. Zingg

2007-01-01

279

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

PubMed

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

Kumar, Abhay; Majeti, Narasimha Vara Prasad

2014-07-01

280

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

PubMed Central

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.

2013-01-01

281

iRootHair: a comprehensive root hair genomics database.  

PubMed

The specialized root epidermis cells of higher plants produce long, tubular outgrowths called root hairs. Root hairs play an important role in nutrient and water uptake, and they serve as a valuable model in studies of plant cell morphogenesis. More than 1,300 articles that describe the biological processes of these unique cells have been published to date. As new fields of root hair research are emerging, the number of new papers published each year and the volumes of new relevant data are continuously increasing. Therefore, there is a general need to facilitate studies on root hair biology by collecting, presenting, and sharing the available information in a systematic, curated manner. Consequently, in this paper, we present a comprehensive database of root hair genomics, iRootHair, which is accessible as a Web-based service. The current version of the database includes information about 153 root hair-related genes that have been identified to date in dicots and monocots along with their putative orthologs in higher plants with sequenced genomes. In order to facilitate the use of the iRootHair database, it is subdivided into interrelated, searchable sections that describe genes, processes of root hair formation, root hair mutants, and available references. The database integrates bioinformatics tools with a focus on sequence identification and annotation. iRootHair is a unique resource for root hair research that integrates the large volume of data related to root hair genomics in a single, curated, and expandable database that is freely available at www.iroothair.org. PMID:23129204

Kwasniewski, Miroslaw; Nowakowska, Urszula; Szumera, Jakub; Chwialkowska, Karolina; Szarejko, Iwona

2013-01-01

282

Aphidicolin-induced nuclear elongation in tobacco BY-2 cells.  

PubMed

Plant nuclei are known to differentiate into various shapes within a single plant. However, little is known about the mechanisms of nuclear morphogenesis. We found that nuclei of tobacco BY-2 cells were highly elongated on long-term treatment with 5 mg l?¹ aphidicolin, an inhibitor of DNA polymerase ?. In aphidicolin-treated cells, the nuclear length was correlated with the cell length. During culture in the presence of aphidicolin, the nuclei were elongated in parallel with cell elongation. Nuclear elongation was inhibited by the inhibition of cell elongation with 2,6-dichlorobenzonitrile, a cellulose synthesis inhibitor. However, cell elongation induced in the auxin-depleted medium in the absence of aphidicolin did not cause nuclear elongation, indicating that cell elongation alone is not sufficient for nuclear elongation. Treatment with either latrunculin B or propyzamide inhibited the aphidicolin-induced nuclear elongation, indicating that both actin filaments and microtubules (MTs) are required for nuclear elongation. Observations using BY-YTHCLR2 cells, in which actin filaments, MTs and nuclei were simultaneously visualized, revealed that the longitudinally arranged MT bundles associated with the nucleus play an important role in nuclear elongation, and that actin filaments affect the formation of these MT bundles. In aphidicolin-treated cells, the nuclear DNA contents of the elongated nuclei exceeded 4C, and the nuclear length was highly correlated with the nuclear DNA content. In cells treated with 50 mg l?¹ aphidicolin, cells were elongated and nucleus-associated longitudinal MT bundles were formed, but the nuclear DNA contents did not exceed 4C and the nuclei did not elongate. These results indicate that an increase in the nuclear DNA content above 4C is also required for nuclear elongation. PMID:24492257

Yasuhara, Hiroki; Kitamoto, Kazuki

2014-05-01

283

A method to separate plant roots from soil and analyze root surface area  

Microsoft Academic Search

Analysis of the effects of soil management practices on crop production requires knowledge of these effects on plant roots.\\u000a Much time is required to wash plant roots from soil and separate the living plant roots from organic debris and previous years’\\u000a roots. We developed a root washer that can accommodate relatively large soil samples for washing. The root washer has

J. G. Benjamin; D. C. Nielsen

2004-01-01

284

Comparative assessment of time-related bioactive glass and calcium hydroxide effects on mechanical properties of human root dentin.  

PubMed

Suspensions of micro- or nanoparticulate SiO(2)-Na(2)O-CaO-P(2)O(5) bioactive glasses could potentially be used as dressings in traumatized front teeth with open apices as an alternative to Ca(OH)(2). These materials have a disinfecting capacity similar to Ca(OH)(2), but bear the advantage of bioactivity. However, because bioactive glasses initially act as alkaline biocides just as Ca(OH)(2) does, they may also negatively affect mechanical dentin properties over time. This was assessed in the current study using standardized human root dentin bars. Specimens were immersed in 1:20 (wt vol(-1)) suspensions of nanometric bioactive glass 45S5 or calcium hydroxide for 1, 10, or 30 days. Control specimens were immersed in pure saline for 30 days (n = 20 per group). Subsequently, modulus of elasticity (E) and flexural strength (FS) of the specimens were determined. Results were compared between groups using one-way anova and Scheffé's post-hoc test. Ca(OH)(2) caused a significant (P < 0.001) 35% drop in mean flexural strength values compared to the control treatment after 10 days. No further change was observed between 10 days and 30 days. Bioactive glass caused a 20% drop in mean flexural strength as compared to the control after 10 days. However, this difference did not reach statistical significance (P > 0.05). No effects of either material on dentin modulus of elasticity values were observed. It was concluded that the calcium hydroxide suspension affected the dentin more than the bioactive glass counterpart; however, the effect was self-limiting and probably restricted to superficial dentin layers, as suggested by the mere decrease in flexural strength but not in modulus of elasticity values. PMID:19208025

Marending, Monika; Stark, Wendelin J; Brunner, Tobias J; Fischer, Jens; Zehnder, Matthias

2009-02-01

285

Root growth is modulated by differential hormonal sensitivity in neighboring cells  

PubMed Central

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

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

2014-01-01

286

Gel-free proteomic analysis of soybean root proteins affected by calcium under flooding stress  

PubMed Central

Soybean is sensitive to flooding stress and exhibits reduced growth under flooding conditions. To better understand the flooding-responsive mechanisms of soybean, the effect of exogenous calcium on flooding-stressed soybeans was analyzed using proteomic technique. An increase in exogenous calcium levels enhanced soybean root elongation and suppressed the cell death of root tip under flooding stress. Proteins were extracted from the roots of 4-day-old soybean seedlings exposed to flooding stress without or with calcium for 2 days and analyzed using gel-free proteomic technique. Proteins involved in protein degradation/synthesis/posttranslational modification, hormone/cell wall metabolisms, and DNA synthesis were decreased by flooding stress; however, their reductions were recovered by calcium treatment. Development, lipid metabolism, and signaling-related proteins were increased in soybean roots when calcium was supplied under flooding stress. Fermentation and glycolysis-related proteins were increased in response to flooding; however, these proteins were not affected by calcium supplementation. Furthermore, urease and copper chaperone proteins exhibited similar profiles in 4-day-old untreated soybeans and 4-day-old soybeans exposed to flooding for 2 days in the presence of calcium. These results suggest that calcium might affect the cell wall/hormone metabolisms, protein degradation/synthesis, and DNA synthesis in soybean roots under flooding stress. PMID:25368623

Oh, MyeongWon; Nanjo, Yohei; Komatsu, Setsuko

2014-01-01

287

Strigolactones Stimulate Internode Elongation Independently of Gibberellins1[C][W  

PubMed Central

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

2013-01-01

288

Comparison of the early response to aluminum stress between tolerant and sensitive wheat cultivars: Root growth, aluminum content and efflux of K+  

Microsoft Academic Search

In order to characterize the mechanism of Al tolerance (Atlas 66) and Al sensitivity (Scout 66) in two cultivars of wheat (Triticum aestivum L.), the early responses to Al stress under acidic conditions were investigated. Marked inhibition of root elongation of Scout was observed upon treatment with 10 ?M AlCl3 for less than 3 h. The inhibition of root elongation

M. Sasaki; M. Kasai; Y. Yamamoto; H. Matsumoto

1994-01-01

289

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

2013-10-01

290

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

2007-12-01

291

Induction of ELF transmembrane potentials in relation to power-frequency electric field bioeffects in a plant root model system. I. Relationship between applied field strength and cucurbitaceous root growth rates.  

PubMed

Seminal roots of Cucumis sativus and Cucurbita maxima were exposed to 60 Hz electric fields of 100-500 V X m-1 in a conducting aqueous inorganic growth medium. Root growth rates were measured to produce a dose-response relationship for each species. The species were selected for study because of their familial relationship, reported sensitivity to 60 Hz, 360 V X m-1 electric fields, and differing average root cell sizes. The latter characteristic influences the magnitude of ELF membrane potentials induced by constant-strength applied electric fields, but does not affect the magnitude of the electric field strength tangent to the cell surface. The difference in average root cell size between C. sativus (smaller cells) and C. maxima (larger cells) was used to evaluate two alternate hypotheses that the observed effect on root growth is stimulated by the electric field tangent to the cell surface, or a field-induced perturbation in the normal transmembrane potential of the cells. The results of the dose-response relationship studies are qualitatively consistent with the hypothesis that the effect is elicited by induced transmembrane potentials. The smaller-celled roots showed a substantially higher response threshold [C. sativus; E0TH approximately 330 V X m-1] than did the larger-celled species [C. maxima; E0TH approximately 200 V X m-1]. At field strengths above the response thresholds in both species, the growth rate of C. sativus roots was less affected than that of C. maxima roots exposed to the same field strength. PMID:3763827

Brayman, A A; Miller, M W

1986-01-01

292

A kinetic analysis of hyponastic growth and petiole elongation upon ethylene exposure in Rumex palustris  

PubMed Central

Background and Aims Complete submergence is an important stress factor for many terrestrial plants, and a limited number of species have evolved mechanisms to deal with these conditions. Rumex palustris is one such species and manages to outgrow the water, and thus restore contact with the atmosphere, through upward leaf growth (hyponasty) followed by strongly enhanced petiole elongation. These responses are initiated by the gaseous plant hormone ethylene, which accumulates inside plants due to physical entrapment. This study aimed to investigate the kinetics of ethylene-induced leaf hyponasty and petiole elongation. Methods Leaf hyponasty and petiole elongation was studied using a computerized digital camera set-up followed by image analyses. Linear variable displacement transducers were used for fine resolution monitoring and measurement of petiole growth rates. Key Results We show that submergence-induced hyponastic growth and petiole elongation in R. palustris can be mimicked by exposing plants to ethylene. The petiole elongation response to ethylene is shown to depend on the initial angle of the petiole. When petiole angles were artificially kept at 0°, rather than the natural angle of 35°, ethylene could not induce enhanced petiole elongation. This is very similar to submergence studies and confirms the idea that there are endogenous, angle-dependent signals that influence the petiole elongation response to ethylene. Conclusions Our data suggest that submergence and ethylene-induced hyponastic growth and enhanced petiole elongation responses in R. palustris are largely similar. However, there are some differences that may relate to the complexity of the submergence treatment as compared with an ethylene treatment. PMID:20603244

Heydarian, Zohreh; Sasidharan, Rashmi; Cox, Marjolein C. H.; Pierik, Ronald; Voesenek, Laurentius A. C. J.; Peeters, Anton J. M.

2010-01-01

293

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. PMID:23840182

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

2013-01-01

294

Tip growth patterns and growth rates of root hairs on ‘Tamar’ white clover (Trifolium repens L.) in low ionic strength culture solution  

Microsoft Academic Search

A flow?through, low ionic strength nutrient solution system was used in four experiments to establish elongation rates, time to maximum length of individual root hairs, and temporal changes in length in small populations of root hairs in a genotype from a population of cv ‘Tamar’ white clover (Trifolium repens L.) previously selected for long root hairs. Young root hairs showed

D. A. Care; J. R. Crush

2004-01-01

295

Elongation factor-2: a useful gene for arthropod phylogenetics.  

PubMed

Robust resolution of controversial higher-level groupings within Arthropoda requires additional sources of characters. Toward this end, elongation factor-2 sequences (1899 nucleotides) were generated from 17 arthropod taxa (5 chelicerates, 6 crustaceans, 3 hexapods, 3 myriapods) plus an onychophoran and a tardigrade as outgroups. Likelihood and parsimony analyses of nucleotide and amino acid data sets consistently recovered Myriapoda and major chelicerate groups with high bootstrap support. Crustacea + Hexapoda (= Pancrustacea) was recovered with moderate support, whereas the conflicting group Myriapoda + Hexapoda (= Atelocerata) was never recovered and bootstrap values were always <5%. With additional nonarthropod sequences included, one indel supports monophyly of Tardigrada, Onychophora, and Arthropoda relative to molluscan, annelidan, and mammalian outgroups. New and previously published sequences from RNA polymerase II (1038 nucleotides) and elongation factor-1alpha (1092 nucleotides) were analyzed for the same taxa. A comparison of bootstrap values from the three genes analyzed separately revealed widely varying values for some clades, although there was never strong support for conflicting groups. In combined analyses, there was strong bootstrap support for the generally accepted clades Arachnida, Arthropoda, Euchelicerata, Hexapoda, and Pycnogonida, and for Chelicerata, Myriapoda, and Pancrustacea, whose monophyly is more controversial. Recovery of some additional groups was fairly robust to method of analysis but bootstrap values were not high; these included Pancrustacea + Chelicerata, Hexapoda + Cephalocarida + Remipedia, Cephalocarida + Remipedia, and Malaocostraca + Cirripedia. Atelocerata (= Myriapoda + Hexapoda) was never recovered. Elongation factor-2 is now the second protein-encoding, nuclear gene (in addition to RNA polymerase II) to support Pancrustacea over Atelocerata. Atelocerata is widely cited in morphology-based analyses, and the discrepancy between results derived from molecular and morphological data deserves greater attention. PMID:11421654

Regier, J C; Shultz, J W

2001-07-01

296

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

297

Pericycle Cell Proliferation and Lateral Root Initiation in Arabidopsis1  

PubMed Central

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 differentiation zones. However, only some of the dividing pericycle cells are committed to the asymmetric, formative divisions that give rise to lateral root primordia (LRPs). This was demonstrated by direct observation and mapping of mitotic figures, cell-length measurements, and the histochemical analysis of a cyclin-GUS fusion protein in pericycle cells. The estimated duration of a pericycle cell cycle in the root apical meristem was similar to the interval between cell displacement from the meristem and the initiation of LRP formation. Developmentally controlled LRP initiation occurs early, 3 to 8 mm from the root tip. Thus the first growth control point in lateral root formation is defined by the initiation of primordia in stochastic patterns by cells passing through the elongation and young differentiation zones, up to where lateral roots begin to emerge from the primary root. Therefore, the first growth control point is not restricted to a narrow developmental window. We propose that late LRP initiation is developmentally unrelated to the root apical meristem and is operated by a second growth control point that can be activated by environmental cues. The observation that pericycle cells divide and lateral root primordia form without intervening mitotic quiescence suggests that lateral organ formation in roots and shoots might not be as fundamentally different as previously thought. PMID:11115882

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

2000-01-01

298

Pericycle cell proliferation and lateral root initiation in Arabidopsis.  

PubMed

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 differentiation zones. However, only some of the dividing pericycle cells are committed to the asymmetric, formative divisions that give rise to lateral root primordia (LRPs). This was demonstrated by direct observation and mapping of mitotic figures, cell-length measurements, and the histochemical analysis of a cyclin-GUS fusion protein in pericycle cells. The estimated duration of a pericycle cell cycle in the root apical meristem was similar to the interval between cell displacement from the meristem and the initiation of LRP formation. Developmentally controlled LRP initiation occurs early, 3 to 8 mm from the root tip. Thus the first growth control point in lateral root formation is defined by the initiation of primordia in stochastic patterns by cells passing through the elongation and young differentiation zones, up to where lateral roots begin to emerge from the primary root. Therefore, the first growth control point is not restricted to a narrow developmental window. We propose that late LRP initiation is developmentally unrelated to the root apical meristem and is operated by a second growth control point that can be activated by environmental cues. The observation that pericycle cells divide and lateral root primordia form without intervening mitotic quiescence suggests that lateral organ formation in roots and shoots might not be as fundamentally different as previously thought. PMID:11115882

Dubrovsky, J G; Doerner, P W; Colón-Carmona, A; Rost, T L

2000-12-01

299

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

PubMed

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

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

2014-11-01

300

Trade studies of plasma elongation for next-step tokamaks  

SciTech Connect

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

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

1988-09-01

301

Purification and partial amino acid sequencing of a mycorrhiza-related chitinase isoform from Glomus mosseae-inoculated roots of Pisum sativum L.  

PubMed

Colonization of Pisum sativum L. cv. Frisson roots with the arbuscular mycorrhizal fungus Glomus mosseae leads to the induction of four acidic symbiosis-related chitinase (SR-chi) isoforms (EC 3.2.1.14). These isoforms were characterized as 30-kDa proteins with isoelectric points ranging between 5.2 and 5.85. One of these SR-chis was purified by affinity and anion-exchange chromatographies, and isoelectric focusing electrophoresis. The sequences of four internal peptides were obtained. They showed high homology to a class-I chitinase isoform from pea shoots. Parts of the conserved regions of class-I chitinases were found in this SR-chi. This result strongly supports the argument that this SR-chi isoform is of plant origin. The functional role of the SR-chis in arbuscular mycorrhizal symbiosis is discussed. PMID:11678283

Slezack, S; Negrel, J; Bestel-Corre, G; Dumas-Gaudot, E; Gianinazzi, S

2001-09-01

302

Alteration of flavonoid accumulation patterns in transparent testa mutants disturbs auxin transport, gravity responses, and imparts long-term effects on root and shoot architecture.  

PubMed

Flavonoids have broad cross-kingdom biological activity. In Arabidopsis, flavonoid accumulation in specific tissues, notably the root elongation zone and root/shoot junction modulate auxin transport, affect root gravitropism, and influence overall plant architecture. The relative contribution made by aglycones and their glycosides remains undetermined, and the longer-term phenotypic effects of altered flavonoid accumulation are not fully assessed. We tested Arabidopsis thaliana mutants that accumulate different flavonoids to determine which flavonoids were causing these affects. Tandem mass spectrometry and in situ fluorescence localisation were used to determine the in vivo levels of aglycones in specific tissues of 11 transparent testa mutants. We measured rootward and shootward auxin transport, gravitropic responses, and identified the long-term changes to root and shoot architecture. Unexpected aglycone species accumulated in vivo in several flavonoid-pathway mutants, and lower aglycone levels occurred in transcription factor mutants. Mutants accumulating more quercetin and quercetin-glycosides changed the greatest in auxin transport, gravitropism, and aerial tissue growth. Early flavonoid-pathway mutants showed aberrant lateral root initiation patterns including clustered lateral root initiations at a single site. Transcription factor mutants had multiple phenotypes including shallow root systems. These results confirm that aglycones are present at very low levels, show that lateral root initiation is perturbed in early flavonoid-pathway mutants, and indicate that altered flavonoid accumulation affects multiple aspects of plant architecture. PMID:23624937

Buer, Charles S; Kordbacheh, Farzanah; Truong, Thy T; Hocart, Charles H; Djordjevic, Michael A

2013-07-01

303

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

NASA Astrophysics Data System (ADS)

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

Wolverton, Chris

304

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

305

Restored river corridors: first results on the effects of flow variability on vegetation cuttings survival rate and related root architecture  

Microsoft Academic Search

Understanding and predicting the evolution of river alluvial bed forms toward a vegetated or a non-vegetated morphology have important implications for restored river corridors and the related ecosystem functioning (see also Schäppi et al, this session). Vegetation recruitment and growth on non-cohesive material of river corridors, such as gravel bars and islands of braided river, depend on the ability of

N. Pasquale; P. Perona; Z. Jiang; P. Burlando

2009-01-01

306

Ethylene modulates flavonoid accumulation and gravitropic responses in roots of Arabidopsis.  

PubMed

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. PMID:16489132

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

2006-04-01

307

Root gravitropism: a complex response to a simple stimulus?  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

308

Molecular Mobility of Soft Segment of Polyurethane Elastomers under Elongation  

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

309

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

310

Cellulose Orientation in the Outer Epidermal Wall of Angiosperm Roots: Implications for Biosystematics  

PubMed Central

The net orientation of cellulose fibrils in the outer epidermal wall of the root elongation zone of 57 angiosperm species belonging to 29 families was determined by means of Congo Red fluorescence and polarization confocal microscopy. The angiosperms can be divided in three groups. In all but four plant families, the net orientation of the cellulose fibrils is transverse to the root axis. Three families, the Poaceae, Juncaceae and Cyperaceae, have a totally different organization. In the root elongation zone of these plants, the net orientation of cellulose fibrils in the outer epidermal wall is parallel with the root axis. In roots of one family, the Arecaceae, an elongation zone in the literal sense of the word is absent and cellulose fibrils are randomly oriented. PMID:12466108

KERSTENS, SVEN; VERBELEN, JEAN?PIERRE

2002-01-01

311

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

PubMed

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

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

2013-07-01

312

Biophysical Limitation of Cell Elongation in Cereal Leaves  

PubMed Central

Grass leaves grow from the base. Unlike those of dicotyledonous plants, cells of grass leaves expand enclosed by sheaths of older leaves, where there is little or no transpiration, and go through developmental stages in a strictly linear arrangement. The environmental or developmental factor that limits leaf cell expansion must do so through biophysical means at the cellular level: wall?yielding, water uptake and solute supply are all candidates. This Botanical Briefing looks at the possibility that tissue hydraulic conductance limits cell expansion and leaf growth. A model is presented that relates pathways of water movement in the elongation zone of grass leaves to driving forces for water movement and to anatomical features. The bundle sheath is considered as a crucial control point. The relative importance of these pathways for the regulation of leaf growth and for the partitioning of water between expansion and transpiration is discussed. PMID:12197513

FRICKE, WIELAND

2002-01-01

313

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

PubMed

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

Rich, Sarah M; Watt, Michelle

2013-03-01

314

Carbon Cost of the Fungal Symbiont Relative to Net Leaf P Accumulation in a Split-Root VA Mycorrhizal Symbiosis 1  

PubMed Central

Translocation of 14C-photosynthates to mycorrhizal (+ +), half mycorrhizal (0+), and nonmycorrhizal (00) split-root systems was compared to P accumulation in leaves of the host plant. Carrizo citrange seedlings (Poncirus trifoliata [L.] Raf. × Citrus sinensis [L.] Osbeck) were inoculated with the vesicular-arbuscular mycorrhizal fungus Glomus intraradices Schenck and Smith. Plants were exposed to 14 CO2 for 10 minutes and ambient air for 2 hours. Three to 4% of recently labeled photosynthate was allocated to metabolism of the mycorrhiza in each inoculated root half independent of shoot P concentration, growth response, and whether one or both root halves were colonized. Nonmycorrhizal roots respired more of the label translocated to them than did mycorrhizal roots. Label recovered in the potting medium due to exudation or transport into extraradical hyphae was 5 to 6 times greater for (+ +) versus (00) plants. In low nutrient media, roots of (0+) and (+ +) plants transported more P to leaves per root weight than roots of (00) plants. However, when C translocated to roots utilized for respiration, exudation, etc., as well as growth is considered, (00) plant roots were at least as efficient at P uptake (benefit) per C utilized (cost) as (0+) and (+ +) plants. Root systems of (+ +) plants did not supply more P to leaves than (0+) plants in higher nutrient media, yet they still allocated twice the 14C-photosynthate to the mycorrhiza as did (0+) root systems. This indicates there is an optimal level of mycorrhizal colonization above which the plant receives no enhanced P uptake yet continues to partition photosynthates to metabolism of the mycorrhiza. PMID:16665934

Douds, David D.; Johnson, Charles R.; Koch, Karen E.

1988-01-01

315

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

316

Fatty Acid-Elongating Activity in Rapidly Expanding Leek Epidermis.  

PubMed Central

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

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

1995-01-01

317

A Chemical Kinetic Model of Transcriptional Elongation  

E-print Network

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

Yujiro Richard Yamada; Charles S. Peskin

2006-03-12

318

Germination and elongation of flax in microgravity  

NASA Astrophysics Data System (ADS)

This experiment was conducted as part of a risk mitigation payload aboard the Space Shuttle Atlantis on STS-101. The objectives were to test a newly developed water delivery system, and to determine the optimal combination of water volume and substrate for the imbibition and germination of flax ( Linum usitatissimum) seeds in space. Two different combinations of germination paper were tested for their ability to absorb, distribute, and retain water in microgravity. A single layer of thick germination paper was compared with one layer of thin germination paper under a layer of thick paper. Paper strips were cut to fit snugly into seed cassettes, and seeds were glued to them with the micropyle ends pointing outward. Water was delivered in small increments that traveled through the paper via capillary action. Three water delivery volumes were tested, with the largest (480 ?L) outperforming the 400 ?L, and 320 ?L volumes for percent germination (90.6%) and root growth (mean = 4.1 mm) during the 34-hour spaceflight experiment. The ground control experiment yielded similar results, but with lower rates of germination (84.4%) and shorter root lengths (mean = 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 thick germination paper generally exhibited better overall growth than the two layered option. Significant seed position effects were observed in both the flight and ground control experiments. Overall, the design of the water delivery system, seed cassettes and the germination paper strip concept was validated as an effective method for promoting seed germination and root growth under microgravity conditions.

Levine, Howard G.; Anderson, Ken; Boody, April; Cox, Dave; Kuznetsov, Oleg A.; Hasenstein, Karl H.

2003-05-01

319

Aluminium Toxicity in Rye (Secale cereale): Root Growth and Dynamics of Cytoplasmic Ca2+ in Intact Root Tips  

PubMed Central

Aluminium (Al) toxicity in rye (Secale cereale L.), an Al?resistant crop, was examined by measuring root elongation and cytoplasmic free activity of calcium ([Ca2+]cyt) in intact root apical cells. Measurement of [Ca2+]cyt was achieved by loading a Ca2+?sensitive fluorescent probe, Fluo?3/AM ester, into root apical cells followed by detection of intracellular fluorescence using a confocal laser scanning microscope. After 20 min of exposure to 50 µm Al (pH 4·2) a slight increase in [Ca2+]cyt of root apical cells was observed, while the response of [Ca2+]cyt to 100 µm Al (pH 4·2) was faster and larger ([Ca2+]cyt increased by 46 % in 10 min). Increases in [Ca2+]cyt were correlated with inhibition of root growth, generally measurable after 2 h. Addition of 400 µm malic acid (pH 4·2) largely ameliorated the effect of 100 µm Al on [Ca2+]cyt in root apical cells and protected root growth from Al toxicity. These results suggest that an increase in [Ca2+]cyt in root apical cells in rye is an early effect of Al toxicity and is followed by the secondary effect on root elongation. PMID:12099355

MA, QIFU; RENGEL, ZDENKO; KUO, JOHN

2002-01-01

320

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

321

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

PubMed

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

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

2013-10-01

322

Brownian motion in a fluid in elongational flow  

SciTech Connect

Brownian motion of a spherical particle in stationary elongational flow is studied. We derive the Langevin equation together with the fluctuation-dissipation theorem for the particle from nonequilibrium fluctuating hydrodynamics to linear order in the elongation-rate-dependent inverse penetration depths. We then analyze how the velocity autocorrelation function as well as the mean square displacement are modified by the elongational flow. We find that for times small compared to the inverse elongation rate the behavior is similar to that found in the absence of the elongational flow. Upon approaching times comparable to the inverse elongation rate the behavior changes and one passes into a time domain where it becomes fundamentally different. In particular, we discuss the modification of the t/sup -3/2/ long-time tail of the velocity autocorrelation function and comment on the resulting contribution to the mean square displacement. The possibility of defining a diffusion coefficient in both time domains is discussed.

Rubi, J.M.; Bedeaux, D.

1988-10-01

323

Temperature influences on root growth for Encelia farinosa (Asteraceae), Pleuraphis rigida (Poaceae), and Agave deserti (Agavaceae) under current and doubled CO{sub 2} concentrations  

SciTech Connect

To help evaluate root distribution patterns, elongation rates of individual roots were measured as a function of soil temperature for Encelia farinosa (a C{sub 3} species), Pleuraphis rigida (C{sub 4}), and Agave deserti (CAM), sympatric codominants in the northwestern Donoran Desert. Measurements were made at current and doubled CO{sub 2} concentrations under winter and summer conditions of air temperature (day/night temperatures of 17 C/10 C and 33 C/22 C, respectively). The three species had different optimal temperatures for root elongation (T{sub opt}) under winter conditions (25 C for E. farinosa, 35 C for P. rigida, and 30 C for A. deserti); T{sub opt} increased by 2-3 C under summer conditions for all three species. The limiting temperatures for elongation also acclimated from winter to summer conditions. The rate of root elongation at T{sub opt} was higher under summer than winter conditions for E. farinosa and P. rigida reflecting conditions for maximum photosynthesis; no difference occurred for A. deserti. Decreased elongation rates at extreme temperatures were associated with less cell division and reduced cell extension. The doubled CO{sub 2} concentration increased average daily root elongation rates for A. deserti under both winter (7%) and summer (12%) conditions, but had no effect for the other two species. Simulations of root elongation as a function of soil temperatures showed that maximum elongation would occur at different depths and during different seasons, contributing to their niche separation. Shading of the soil surface moderated daily variations in soil temperature, reducing seasonal root elongation for winter and spring and increasing elongation for summer. Shading also altered root distribution patterns, e.g., optimal rooting depth for A. deserti and especially P. rigida increased for a hot summer day. 34 refs., 3 figs., 1 tab.

Drennan, P.M.; Nobel, P.S. [Univ. of California, Los Angeles, CA (United States)

1996-02-01

324

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

325

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

PubMed Central

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

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

1998-01-01

326

Growth, water relations and solute accumulation in osmotically stressed seedlings of the tropical tree Colophospermum mopane.  

PubMed

Root and hypocotyl elongation, water status and solute accumulation were studied in osmotically stressed seedlings of the tropical tree, Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Léonard, which grows in hot arid areas of southern and central Africa. Seeds were imbibed for 24 h and then subjected to a polyethylene-glycol-generated osmotic stress of -0.03 (control), -0.2, -0.8, -1.6 or -2.0 MPa for 60 h. Seedlings subjected to moderate water stress (-0.2 MPa) had higher root growth rates (2.41 +/- 0.24 mm h(-1)), greater final root lengths (111 +/- 3.8 mm) and longer cells immediately behind the root elongation zone than control seedlings (1.70 +/- 0.15 mm h(-1) and 93 +/- 3.9 mm, respectively). Root lengths of seedlings in the -0.8 and -1.6 MPa treatments were similar to those of control seedlings, whereas the -2.0 MPa seedlings had significantly shorter roots. Both root and hypocotyl tissues exhibited considerable osmotic adjustment to the external water potential treatments. Seedlings in the -0.03, -0.2, and -0.8 MPa treatments had similar cell turgor pressures (0.69 +/- 0.10, 0.68 +/- 0.07 and 0.57 +/- 0.04 MPa, respectively), whereas the -2.0 MPa treatment lowered cell turgor pressure to 0.17 +/- 0.04 MPa. Root vacuolar osmotic pressures were generally similar to sap osmotic pressures, indicating that the increased root elongation observed in moderately water-stressed seedlings was not caused by increased turgor pressure difference. Neutral-fraction solute concentrations, including the osmoticum pinitol, increased approximately two-fold in root sap in response to a low external water potential. In hypocotyl sap of seedlings in the -2.0 MPa treatment, pinitol more than doubled, sucrose increased from about 2 to 75 mol m(-3) but glucose and fructose remained unchanged and, as a result, total sugars increased only slightly. The benefits of rapid early root elongation and osmoticum accumulation under conditions of water stress are discussed in relation to seedling establishment. PMID:14871694

Johnson, J M; Pritchard, J; Gorham, J; Tomos, A D

1996-08-01

327

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

PubMed

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

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

2014-01-15

328

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

NASA Technical Reports Server (NTRS)

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

Thomas, J. F.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

1985-01-01

329

(R)-?-Lysine-modified Elongation Factor P Functions in Translation Elongation*  

PubMed Central

Post-translational modification of bacterial elongation factor P (EF-P) with (R)-?-lysine at a conserved lysine residue activates the protein in vivo and increases puromycin reactivity of the ribosome in vitro. The additional hydroxylation of EF-P at the same lysine residue by the YfcM protein has also recently been described. The roles of modified and unmodified EF-P during different steps in translation, and how this correlates to its physiological role in the cell, have recently been linked to the synthesis of polyproline stretches in proteins. Polysome analysis indicated that EF-P functions in translation elongation, rather than initiation as proposed previously. This was further supported by the inability of EF-P to enhance the rate of formation of fMet-Lys or fMet-Phe, indicating that the role of EF-P is not to specifically stimulate formation of the first peptide bond. Investigation of hydroxyl-(?)-lysyl-EF-P showed 30% increased puromycin reactivity but no differences in dipeptide synthesis rates when compared with the ?-lysylated form. Unlike disruption of the other genes required for EF-P modification, deletion of yfcM had no phenotypic consequences in Salmonella. Taken together, our findings indicate that EF-P functions in translation elongation, a role critically dependent on post-translational ?-lysylation but not hydroxylation. PMID:23277358

Bullwinkle, Tammy J.; Zou, S. Betty; Rajkovic, Andrei; Hersch, Steven J.; Elgamal, Sara; Robinson, Nathaniel; Smil, David; Bolshan, Yuri; Navarre, William Wiley; Ibba, Michael

2013-01-01

330

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

331

Expression of GFP-actin leads to failure of nuclear elongation and cytokinesis in Tetrahymena thermophila.  

PubMed

Green fluorescent protein (GFP)-tagged actin was used to investigate the distribution and function of actin in Tetrahymena. A strain that expresses both GFP-actin and endogenous actin was developed by transformation of Tetrahymena thermophila with a ribosomal DNA-based replicative vector. Confocal microscopy of living cells and immunogold electron microscopy confirmed localization of GFP-actin to basal bodies and the contractile ring. Incorporation of the fusion protein into these and other actin-related structures correlated with severe impairment of macronuclear elongation and cytokinesis. At 30 degrees C macronuclear elongation failed to occur in 25% of the transformants despite completion of micronuclear division. At 20 degrees C macronuclear elongation failed to occur in 2% of the population. Arrest of cytokinesis coincided with failure of macronuclear elongation. Arrested cells developed into homopolar doublets with two sets of oral structures. This study indicates a requirement for actin in nuclear elongation and cytokinesis. Although GFP-actin can interfere with the functioning of actin-containing structures, the GFP-actin transformant strain can be used to monitor actin distribution and dynamics and is therefore an important new tool for further studies of Tetrahymena actin. PMID:14733431

Hosein, Roland E; Williams, Selwyn A; Haye, Kester; Gavin, R H

2003-01-01

332

Shape elongation of Zn nanoparticles in silica irradiated with swift heavy ions of different species and energies: scaling law and some insights on the elongation mechanism.  

PubMed

Zinc nanoparticles (NPs) embedded in silica were irradiated with swift heavy ions (SHIs) of seven different combinations of species and energies. The shape elongation induced by the irradiations was evaluated by optical linear dichroism (OLD) spectroscopy, which is a sensitive tool for determining the change in the mean aspect ratio (AR) of NPs. Although the mean AR change indicated a linear fluence dependence in the low- and medium-fluence regions, it indicated a nonlinear dependence in the high-fluence region. The data reveal that the elongation efficiency of Zn is correlated with the electronic stopping power 'Se in silica' and is not correlated with either the 'Se in Zn' or the nuclear stopping power. The elongation efficiency plotted as a function of the 'Se in silica' revealed a linear relationship, with a threshold value of ?2 keV nm(-1), which is the same dependence exhibited by the ion-track formation in silica. The log-log plot showed that the elongation efficiency increased linearly with Se above a critical value of ?3 keV nm(-1) and steeply decreased with Se to the power of 5 below the critical Se. The steep decrease can be ascribed to the discontinuous nature of the ion tracks, which is expected at Se ? 2-4 keV nm(-1) in silica. The fluence ? dependences of AR - 1 under various irradiations are well-normalized with the electronic energy deposition of SHIs, i.e., the product of Se and ?, with a Se greater than the same critical value of ?3 keV nm(-1). The normalized data above the critical value fell on a linear relation, AR(?) - 1  ? Se?, for Se? < 2 keV nm(-3) and a sublinear relation, AR(?) - 1 ? (Se?)(1/2) for Se? > 2 keV nm(-3). On the basis of these experimental results, we discuss some insights into the elongation mechanism. PMID:25288109

Amekura, H; Mohapatra, S; Singh, U B; Khan, S A; Kulriya, P K; Ishikawa, N; Okubo, N; Avasthi, D K

2014-10-31

333

Control of leaf cell elongation in barley. Generation rates of osmotic pressure and turgor, and growth-associated water potential gradients  

Microsoft Academic Search

.   In a previous study on the effects of N-supply on leaf cell elongation, the spatial distribution of relative cell elongation\\u000a rates (RCER), epidermal cell turgor, osmotic pressure (OP) and water potential (?) along the elongation zone of the third\\u000a leaf of barley was determined (W. Fricke et al. 1997, Planta 202: 522–530). The results suggested that in plants receiving

Wieland Fricke; T. J. Flowers

1998-01-01

334

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

335

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

2013-01-01

336

Regulation of Submergence?induced Enhanced Shoot Elongation in Oryza sativa L.  

PubMed Central

Rice (Oryza sativa L.) is the only cereal that can be cultivated in the frequently flooded river deltas of South?East and South Asia. The survival strategies used by rice have been studied quite extensively and the role of several phytohormones in the elongation response has been established. Deep?water rice cultivars can diminish flooding stress by rapid elongation of their submerged tissues to keep up with the rising waters. Other rice cultivars may react by mechanisms of submergence tolerance. Aerenchyma and aerenchymatous adventitious roots are formed that facilitate oxygen diffusion to prevent anaerobic conditions in the submerged tissues. This paper discusses the molecular aspects of the mechanism that leads to shoot elongation (leaves of seedlings and internodes), the regulation of which involves metabolism of, and interactions between, ethylene, gibberellins and abscisic acid. Finally, the importance of new techniques in future research is assessed. Current molecular technology can reveal subtle differences in gene activity between tolerant and non?tolerant cultivars, and identify genes that are involved in the regulation of submergence avoidance and tolerance. PMID:12509346

VRIEZEN, WIM H.; ZHOU, ZHONGYI; VAN DER STRAETEN, DOMINIQUE

2003-01-01

337

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.

338

Cortical and cap sedimentation in gravitropic Equisetum roots.  

PubMed

Although the rootcap is required for gravitropic sensing, various classical and contemporary data raise the question of whether additional sensing occurs away from the cap in roots. Roots of Equisetum hyemale L. (horsetail) were examined by light and electron microscopy to determine which cell components were distributed with respect to gravity both in and away from the rootcap. Adventitious roots from stem cuttings were gravitropic in a vertical orientation or if reoriented to the horizontal. Obvious amyloplast sedimentation was found in vertical and in reoriented roots 1) in cells in the center of the rootcap and 2) in young, elongating cortical cells located in two to three layers outside the endodermis. These cortical amyloplasts were smaller than cap amyloplasts and, unlike central cap amyloplasts, were occasionally found in the top of the cell. The nucleus was also sedimented on top of the amyloplasts in both cell types, both in vertical and in reoriented roots. Sedimentation of both organelles ceased as cortical cells elongated further or as cap cells became peripheral in location. In both cell types with sedimentation, endoplasmic reticulum was located in the cell periphery, but showed no obvious enrichment near the lower part of the cell in vertical roots. This is the first modern report of sedimentation away from the cap in roots, and it provides structural evidence that gravitropic sensing may not be confined to the cap in all roots. PMID:11537672

Ridge, R W; Sack, F D

1992-03-01

339

Cortical and cap sedimentation in gravitropic Equisetum roots  

NASA Technical Reports Server (NTRS)

Although the rootcap is required for gravitropic sensing, various classical and contemporary data raise the question of whether additional sensing occurs away from the cap in roots. Roots of Equisetum hyemale L. (horsetail) were examined by light and electron microscopy to determine which cell components were distributed with respect to gravity both in and away from the rootcap. Adventitious roots from stem cuttings were gravitropic in a vertical orientation or if reoriented to the horizontal. Obvious amyloplast sedimentation was found in vertical and in reoriented roots 1) in cells in the center of the rootcap and 2) in young, elongating cortical cells located in two to three layers outside the endodermis. These cortical amyloplasts were smaller than cap amyloplasts and, unlike central cap amyloplasts, were occasionally found in the top of the cell. The nucleus was also sedimented on top of the amyloplasts in both cell types, both in vertical and in reoriented roots. Sedimentation of both organelles ceased as cortical cells elongated further or as cap cells became peripheral in location. In both cell types with sedimentation, endoplasmic reticulum was located in the cell periphery, but showed no obvious enrichment near the lower part of the cell in vertical roots. This is the first modern report of sedimentation away from the cap in roots, and it provides structural evidence that gravitropic sensing may not be confined to the cap in all roots.

Ridge, R. W.; Sack, F. D.

1992-01-01

340

Regulated tissue fluidity steers zebrafish body elongation  

PubMed Central

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

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

2013-01-01

341

NATURE CELL BIOLOGY VOLUME 7 | NUMBER 11 | NOVEMBER 2005 1057 Root gravitropism requires lateral root cap and  

E-print Network

a rapid, asymmetric release of the growth regulator auxin from gravity-sensing columella cells at the root changes in their orientation using specialized gravity-sensing cells that are located within the columella columella and elongation-zone tis- sues, that respectively sense6­9 and respond10 to the gravity stimulus

Haseloff, Jim

342

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...

343

Is elongation-induced leaf emergence beneficial for submerged Rumex species?  

PubMed Central

Background and Aims Plant species from various taxa ‘escape’ from low oxygen conditions associated with submergence by a suite of traits collectively called the low oxygen escape syndrome (LOES). The expression of these traits is associated with costs and benefits. Thus far, remarkably few studies have dealt with the expected benefits of the LOES. Methods Young plants were fully submerged at initial depths of 450 mm (deep) or 150–240 mm (shallow). Rumex palustris leaf tips emerged from the shallow flooding within a few days, whereas a slight lowering of shallow flooding was required to expose R. acetosa leaf tips to the atmosphere. Shoot biomass and petiole porosity were measured for all species, and treatments and data from the deep and shallow submergence treatments were compared with non-flooded controls. Key Results R. palustris is characterized by submergence-induced enhanced petiole elongation. R. acetosa lacked this growth response. Upon leaf tip emergence, R. palustris increased its biomass, whereas R. acetosa did not. Furthermore, petiole porosity in R. palustris was twice as high as in R. acetosa. Conclusions Leaf emergence restores gas exchange between roots and the atmosphere in R. palustris. This occurs to a much lesser extent in R. acetosa and is attributable to its lower petiole porosity and therefore limited internal gas transport. Leaf emergence resulting from fast petiole elongation appears to benefit biomass accumulation if these plants contain sufficient aerenchyma in petioles and roots to facilitate internal gas exchange. PMID:18697756

Pierik, R.; van Aken, J. M.; Voesenek, L. A. C. J.

2009-01-01

344

Linear theory of nonisothermal forced elongation Thomas Hagen  

E-print Network

Linear theory of nonisothermal forced elongation Thomas Hagen February 2005 Abstract In this work the linearized equations of nonisothermal forced elonga- tion are analyzed. It is shown that solutions properties of the semigroup correspond to the expected physical behavior of the elongational flow. Key words

Hagen, Thomas

345

Elongational viscosity of monodisperse and bidisperse polystyrene melts  

E-print Network

Elongational viscosity of monodisperse and bidisperse polystyrene melts Jens Kromann Nielsen have been measured for two monodisperse polystyrene melts with molecular weights of 52 and 103 kg/mole, and for three bidisperse polystyrene melts. The monodisperse melts show a maximum in the steady elongational

346

Analysis of cell elongation in red algae by fluorescent labelling  

Microsoft Academic Search

The mechanism of cell elongation in five red algae, Griffithsia pacifica Kylin, G. tenuis C. Agardh, G. globulifera Harvey, Antithamnion kylinii Gardner, and Callithamnion sp. was studied using Calcofluor White ST as a vital, fluorescent cell-wall stain. In each alga elongation of intercalary shoot cells occurs primarily by the localized addition of new cell-wall material rather than by extension of

Susan Drury Waaland; J. Robert Waaland

1975-01-01

347

A Split-Root Technique for Measuring Root Water Potential  

PubMed Central

Water encounters various resistances in moving along a path of decreasing potential energy from the soil through the plant to the atmosphere. The reported relative magnitudes of these pathway resistances vary widely and often these results are conflicting. One reason for such inconsistency is the difficulty in measuring the potential drop across various segments of the soil-plant-atmosphere continuum. The measurement of water potentials at the soil-root interface and in the root xylem of a transpiring plant remains a challenging problem. In the divided root experiment reported here, the measured water potential of an enclosed, nonabsorbing branch of the root system of young corn (Bonanza) plants to infer the water potential of the remaining roots growing in soil was used. The selected root branch of the seedling was grown in a specially constructed Teflon test tube into which a screen-enclosed thermocouple psychrometer was inserted and sealed to monitor the root's water potential. The root and its surrounding atmosphere were assumed to be in vapor equilibrium. Images PMID:16661886

Adeoye, Kingsley B.; Rawlins, Stephen L.

1981-01-01

348

Molecular Phylogeny and Evolution of Parabasalia with Improved Taxon Sampling and New Protein Markers of Actin and Elongation Factor-1?  

PubMed Central

Background Inferring the evolutionary history of phylogenetically isolated, deep-branching groups of taxa—in particular determining the root—is often extraordinarily difficult because their close relatives are unavailable as suitable outgroups. One of these taxonomic groups is the phylum Parabasalia, which comprises morphologically diverse species of flagellated protists of ecological, medical, and evolutionary significance. Indeed, previous molecular phylogenetic analyses of members of this phylum have yielded conflicting and possibly erroneous inferences. Furthermore, many species of Parabasalia are symbionts in the gut of termites and cockroaches or parasites and therefore formidably difficult to cultivate, rendering available data insufficient. Increasing the numbers of examined taxa and informative characters (e.g., genes) is likely to produce more reliable inferences. Principal Findings Actin and elongation factor-1? genes were identified newly from 22 species of termite-gut symbionts through careful manipulations and seven cultured species, which covered major lineages of Parabasalia. Their protein sequences were concatenated and analyzed with sequences of previously and newly identified glyceraldehyde-3-phosphate dehydrogenase and the small-subunit rRNA gene. This concatenated dataset provided more robust phylogenetic relationships among major groups of Parabasalia and a more plausible new root position than those previously reported. Conclusions/Significance We conclude that increasing the number of sampled taxa as well as the addition of new sequences greatly improves the accuracy and robustness of the phylogenetic inference. A morphologically simple cell is likely the ancient form in Parabasalia as opposed to a cell with elaborate flagellar and cytoskeletal structures, which was defined as most basal in previous inferences. Nevertheless, the evolution of Parabasalia is complex owing to several independent multiplication and simplification events in these structures. Therefore, systematics based solely on morphology does not reflect the evolutionary history of parabasalids. PMID:22253832

Noda, Satoko; Mantini, Clea; Meloni, Dionigia; Inoue, Jun-Ichi; Kitade, Osamu; Viscogliosi, Eric; Ohkuma, Moriya

2012-01-01

349

The plant embryo is a relatively simple structure consisting of a primordial shoot and root, whose development is frozen in the  

E-print Network

for the forma- tion of leaves, stem, flowers, roots and other tissues. Secondly, plant cells are surrounded is not possible. Cells are often arranged in sheets or files, and division must therefore be coordinated in some

Murray, J.A.H.

350

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

351

High n ballooning modes in highly elongated tokamaks  

SciTech Connect

An analytic study of stability against high n ballooning modes in highly elongated axisymmetric plasmas is presented and compared with computational results. From the equation for the marginal pressure gradient, it is found that the local shear plays an important role on the stability of elongated and shifted plasma, and that high elongation deteriorates the stability by decreasing the stabilizing effects of field line bending and local shear. The net contribution of the local shear to stability decreases with elongation and shift for strongly ballooning modes (eigenfunctions strongly localized near the outer edge of the toroidal flux surfaces) but increases for interchange modes (eigenfunctions more uniform along the flux surfaces). The computational study of high n ballooning modes in a highly elongated plasma reveals that lowering the aspect ratio and broadening the pressure profile enhance the marginal beta for ..beta../sub p/ less than unity but severely reduce the marginal beta for ..beta../sub p/ larger than unity.

An, C.H.; Bateman, G.

1980-02-01

352

Differential Gene Expression in Brassica rapa Roots After Reorientation and Clinorotation.  

NASA Astrophysics Data System (ADS)

Seedlings align their growth axes parallel to the gravity vector. Any growth adjustment affects genes. We examined these changes in Brassica rapa roots that were reoriented and clinorotated. Gene expression levels related to the actin cytoskeleton (ACT7 and ADK1) and auxin transport (IAA5, PIN1, PIN3, AGR1, ARG1) were assessed in roots grown for 42 hours and then either reoriented to 90° for 15 min, 1, 2 and 3 hours or clinorotated vertically or horizontally for 42 hrs at 2 rpm. After these treatments, roots from 20 seedlings were divided into three sections, the root tip, elongation zone, and maturation zone. The samples from corresponding treatments were combined for RNA extraction, reverse transcription and analysis by quantitative PCR. The results show that gene expression changes in response to duration of reorientation and orientation during clinorotation. All genes, except PIN1 and AGR1 were upregulated in the tip after 2 hours of reorientation. Expression of genes also varied between the root sections except for PIN1, which was uniformly expressed. ADK1 was the only gene that showed consistent down-regulation in all three root regions in vertically and horizontally clinorotated roots (ca 30% of controls). In contrast, ADK1 was upregulated (more than 150 fold) in the tip of roots that were reoriented for 2 hours but little upregulation after one hour (less than 2 fold compared to controls). Our results indicate that gene expression during the gravitropic response changes over time with the tip region being the most dynamic tissue in the root. The large upregulation of ADK1 at 2 h after reorientation may be related to the persistence of the gravitropic response. Because of the variability of the expression profiles, analyses that are based on the entire root miss tissue specific changes in gene expression. Differences in gene expression after vertical and horizontal clinorotation indicates that the graviresponse system is sensitive not just to the magnitude of mechano-stimulation but also the direction. Supported by NASA grant NNX10AP91G and LaSPACE GSRA.

Edge, Andrea; Hasenstein, Karl H.

353

Pseudomonas fluorescens and Glomus mosseae trigger DMI3-dependent activation of genes related to a signal transduction pathway in roots of Medicago truncatula.  

PubMed

Plant genes induced during early root colonization of Medicago truncatula Gaertn. J5 by a growth-promoting strain of Pseudomonas fluorescens (C7R12) have been identified by suppressive subtractive hybridization. Ten M. truncatula genes, coding proteins associated with a putative signal transduction pathway, showed an early and transient activation during initial interactions between M. truncatula and P. fluorescens, up to 8 d after root inoculation. Gene expression was not significantly enhanced, except for one gene, in P. fluorescens-inoculated roots of a Myc(-)Nod(-) genotype (TRV25) of M. truncatula mutated for the DMI3 (syn. MtSYM13) gene. This gene codes a Ca(2+) and calmodulin-dependent protein kinase, indicating a possible role of calcium in the cellular interactions between M. truncatula and P. fluorescens. When expression of the 10 plant genes was compared in early stages of root colonization by mycorrhizal and rhizobial microsymbionts, Glomus mosseae activated all 10 genes, whereas Sinorhizobium meliloti only activated one and inhibited four others. None of the genes responded to inoculation by either microsymbiont in roots of the TRV25 mutant. The similar response of the M. truncatula genes to P. fluorescens and G. mosseae points to common molecular pathways in the perception of the microbial signals by plant roots. PMID:16183836

Sanchez, Lisa; Weidmann, Stéphanie; Arnould, Christine; Bernard, Anne Rose; Gianinazzi, Silvio; Gianinazzi-Pearson, Vivienne

2005-10-01

354

Pseudomonas fluorescens and Glomus mosseae Trigger DMI3-Dependent Activation of Genes Related to a Signal Transduction Pathway in Roots of Medicago truncatula1  

PubMed Central

Plant genes induced during early root colonization of Medicago truncatula Gaertn. J5 by a growth-promoting strain of Pseudomonas fluorescens (C7R12) have been identified by suppressive subtractive hybridization. Ten M. truncatula genes, coding proteins associated with a putative signal transduction pathway, showed an early and transient activation during initial interactions between M. truncatula and P. fluorescens, up to 8 d after root inoculation. Gene expression was not significantly enhanced, except for one gene, in P. fluorescens-inoculated roots of a Myc?Nod? genotype (TRV25) of M. truncatula mutated for the DMI3 (syn. MtSYM13) gene. This gene codes a Ca2+ and calmodulin-dependent protein kinase, indicating a possible role of calcium in the cellular interactions between M. truncatula and P. fluorescens. When expression of the 10 plant genes was compared in early stages of root colonization by mycorrhizal and rhizobial microsymbionts, Glomus mosseae activated all 10 genes, whereas Sinorhizobium meliloti only activated one and inhibited four others. None of the genes responded to inoculation by either microsymbiont in roots of the TRV25 mutant. The similar response of the M. truncatula genes to P. fluorescens and G. mosseae points to common molecular pathways in the perception of the microbial signals by plant roots. PMID:16183836

Sanchez, Lisa; Weidmann, Stephanie; Arnould, Christine; Bernard, Anne Rose; Gianinazzi, Silvio; Gianinazzi-Pearson, Vivienne

2005-01-01

355

Effects of physical connection and genetic identity of neighbouring ramets on root-placement patterns in two clonal species.  

PubMed

Root-placement patterns were examined in the clonal species Glechoma hederacea and Fragaria vesca when grown with different types of neighbours. Three different patterns were predicted as consequences of different types of interactions between roots: the avoidance pattern if root growth decreases in the presence of neighbouring roots; the intrusive pattern if root growth increases towards neighbouring roots; and the unresponsive pattern if root growth is unaffected by neighbouring roots. Experiments were conducted in which physical connection between ramets, and the genetic identity of neighbouring ramets, were manipulated. The patterns of distribution of entire root systems and elongation rates of individual roots were measured. Root systems and individual roots of G. hederacea avoided contact with roots of neighbouring ramets, irrespective of connection to the neighbour and its genetic or specific identity. In contrast, F. vesca roots grew equally towards and away from intraspecific ramet neighbours and their elongation was stimulated by contact with roots of G. hederacea ramets. These results demonstrate that root-placement patterns of plants grown with different types of neighbours vary between species, and suggest that factors additional to resource depletion could be involved in their development. PMID:17850258

Semchenko, Marina; John, Elizabeth A; Hutchings, Michael J

2007-01-01

356

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. PMID:19696888

Pelechano, Vicent; Jimeno-González, Silvia; Rodríguez-Gil, Alfonso; García-Martínez, José; Pérez-Ortín, José E.; Chávez, Sebastián

2009-01-01

357

Expressed Proteins of Herbaspirillum seropedicae in Maize (DKB240) Roots-Bacteria Interaction Revealed Using Proteomics.  

PubMed

Several molecular tools have been used to clarify the basis of plant-bacteria interaction; however, the mechanism behind the association is still unclear. In this study, we used a proteomic approach to investigate the root proteome of Zea mays (cv. DKB240) inoculated with Herbaspirillum seropedicae strain SmR1 grown in vitro and harvested 7 days after inoculation. Eighteen differentially accumulated proteins were observed in root samples, ten of which were identified by MALDI-TOF mass spectrometry peptide mass fingerprint. Among the identified proteins, we observed three proteins present exclusively in inoculated root samples and six upregulated proteins and one downregulated protein relative to control. Differentially expressed maize proteins were identified as hypothetical protein ZEAMMB73_483204, hypothetical protein ZEAMMB73_269466, and tubulin beta-7 chain. The following were identified as H. seropedicae proteins: peroxiredoxin protein, EF-Tu elongation factor protein, cation transport ATPase, NADPH:quinone oxidoreductase, dinitrogenase reductase, and type III secretion ATP synthase. Our results presented the first evidence of type III secretion ATP synthase expression during H. seropedicae-maize root interaction. PMID:25173675

Ferrari, Cibele Santos; Amaral, Fernanda Plucani; Bueno, Jessica Cavalheiro Ferreira; Scariot, Mirella Christine; Valentim-Neto, Pedro Alexandre; Arisi, Ana Carolina Maisonnave

2014-11-01

358

A plausible mechanism for auxin patterning along the developing root  

PubMed Central

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 maintains the stem cell niche. Proximal maxima may trigger lateral or adventitious root initiation. Results We propose a reflected flow mechanism for the formation of the auxin maximum in the root apical meristem. The mechanism is based on auxin's known activation and inhibition of expressed PIN family auxin carriers at low and high auxin levels, respectively. Simulations showed that these regulatory interactions are sufficient for self-organization of the auxin distribution pattern along the central root axis under varying conditions. The mathematical model was extended with rules for discontinuous cell dynamics so that cell divisions were also governed by auxin, and by another morphogen Division Factor which combines the actions of cytokinin and ethylene on cell division in the root. The positional information specified by the gradients of these two morphogens is able to explain root patterning along the central root axis. Conclusion We present here a plausible mechanism for auxin patterning along the developing root, that may provide for self-organization of the distal auxin maximum when the reverse fountain has not yet been formed or has been disrupted. In addition, the proximal maxima are formed under the reflected flow mechanism in response to periods of increasing auxin flow from the growing shoot. These events may predetermine lateral root initiation in a rhyzotactic pattern. Another outcome of the reflected flow mechanism - the predominance of lateral or adventitious roots in different plant species - may be based on the different efficiencies with which auxin inhibits its own transport in different species, thereby distinguishing two main types of plant root architecture: taproot vs. fibrous. PMID:20663170

2010-01-01

359

Effects of root temperature on growth and photosynthesis in conifer seedlings during shoot elongation  

Microsoft Academic Search

Summary Growth and gas exchange characteristics were studied in pine (Pinus sylvestris L.) and spruce (Picea shies Karst.) seedlings grown in hydroponic culture in the presence of N (50 mg 1-l) and transferred at the start of their second growing season to tap water at 5, 8, 12, 16 or 20 \\

E. M. VAPAAVUORI; R. RIKALA; A. RYYPPQ

360

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...

361

Interlaboratory Root Elongation Testing of Toxic Substances on Selected Plant Species.  

National Technical Information Service (NTIS)

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 subs...

H. C. Ratsch

1983-01-01

362

microRNA profiling of root tissues and root forming explant cultures in Medicago truncatula.  

PubMed

Plant root architecture is regulated by the initiation and modulation of cell division in regions containing pluripotent stem cells known as meristems. In roots, meristems are formed early in embryogenesis, in the case of the root apical meristem (RAM), and during organogenesis at the site of lateral root or, in legumes, nodule formation. Root meristems can also be generated in vitro from leaf explants cultures supplemented with auxin. microRNAs (miRNAs) have emerged as regulators of many key biological functions in plants including root development. To identify key miRNAs involved in root meristem formation in Medicago truncatula, we used deep sequencing to compare miRNA populations. Comparisons were made between: (1) the root tip (RT), containing the RAM and the elongation zone (EZ) tissue and (2) root forming callus (RFC) and non-root forming callus (NRFC). We identified 83 previously reported miRNAs, 24 new to M. truncatula, in 44 families. For the first time in M. truncatula, members of conserved miRNA families miR165, miR181 and miR397 were found. Bioinformatic analysis identified 38 potential novel miRNAs. Selected miRNAs and targets were validated using Taqman miRNA assays and 5' RACE. Many miRNAs were differentially expressed between tissues, particularly RFC and NRFC. Target prediction revealed a number of miRNAs to target genes previously shown to be differentially expressed between RT and EZ or RFC and NRFC and important in root development. Additionally, we predict the miRNA/target relationships for miR397 and miR160 to be conserved in M. truncatula. Amongst the predictions, were AUXIN RESPONSE FACTOR 10, targeted by miR160 and a LACCASE-like gene, targeted by miR397, both are miRNA/target pairings conserved in other species. PMID:23572382

Eyles, Rodney P; Williams, Philip H; Ohms, Stephen J; Weiller, Georg F; Ogilvie, Huw A; Djordjevic, Michael A; Imin, Nijat

2013-07-01

363

Modelling of Temperature?controlled Internode Elongation Applied to Chrysanthemum  

PubMed Central

The DIF concept states that equal internode length can be achieved with the same difference between day and night temperature irrespective of the mean 24 h temperature. However, the physiological background of the DIF concept is unclear. An attempt to model internode elongation is presented based on three plausible processes, namely (1) the accumulation of elongation requirements during the day, (2) elongation during the night using elongation requirements and (3) the limitation of internode length due to low turgor pressure unable to counter cell wall elasticity. Each reaction rate constant, one per process, depends on temperature according to Arrhenius’ Law. The resulting process?based model describes internode elongation in time and was calibrated on a chrysanthemum data set. Chrysanthemum plants were grown in growth chambers with rigorously defined day and night temperatures. In total, 16 temperature treatments were applied, resulting from the combination of four day and four night temperatures (16, 20, 24 and 28 °C). Internode elongation was measured for the tenth internode in ten plants per treatment. The percentage variance accounted for, R2adj, was almost 91 %. Transferability of model parameters was shown to exist by cross validation. Simulation of the internode length in time as function of mean 24 h temperature and DIF showed that the DIF concept is not apparent after a growing period of 10 d, but is visible after 20 d. This model structure for describing internode elongation might also be applicable for other plants that show the DIF concept. PMID:12234147

SCHOUTEN, R. E.; CARVALHO, S. M. P.; HEUVELINK, E.; VAN KOOTEN, O.

2002-01-01

364

Root gravitropism in response to a signal originating outside of the cap  

NASA Technical Reports Server (NTRS)

We have developed image analysis software linked to a rotating stage, allowing constraint of any user-selected region of a root at a prescribed angle during root gravitropism. This device allows the cap of a graviresponding root to reach vertical while maintaining a selected region within the elongation zone at a gravistimulated angle. Under these conditions gravitropic curvature of roots of Zea mays L. continues long after the root cap reaches vertical, indicating that a signal from outside of the cap can contribute to the curvature response.

Wolverton, Chris; Mullen, Jack L.; Ishikawa, Hideo; Evans, Michael L.

2002-01-01

365

Interactions between abscisic acid, ethylene and gibberellin in internodal elongation in floating rice: the promotive effect of abscisic acid at low humidity  

Microsoft Academic Search

The enhancement of internodal elongation in floating or deepwater rice (Oryza sativa L. cv. Habiganj Aman II) by treatment with ethylene or gibberellic acid (GA3) at high relative humidity (RH) is inhibited by abscisic acid (ABA). Here, we examined the interactive effects of ethylene, gibberellin (GA) and ABA at low RH on internodal elongation of deepwater rice stem segments. Although

Tetsushi Azuma; Tomoko Hatanaka; Naotsugu Uchida; Takeshi Yasuda

2003-01-01

366

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

PubMed Central

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

Luthje, Sabine

2012-01-01

367

Roots and Shoots  

NSDL National Science Digital Library

In this outdoor activity, learners discover that plants aren't just shoots (stem, branches, leaves, and flowers) growing above ground, but contain plenty of roots growing undergroundâmore than half the mass of a plant can be its roots. Learners dig up "mystery" plants to investigate their root structures, and match them to different types of root systems. Learners also learn about animals found near plant roots and how humans use roots.

Science, Lawrence H.

2008-01-01

368

Ethylene-auxin interactions regulate lateral root initiation and emergence in Arabidopsis thaliana.  

PubMed

Plant root systems display considerable plasticity in response to endogenous and environmental signals. Auxin stimulates pericycle cells within elongating primary roots to enter de novo organogenesis, leading to the establishment of new lateral root meristems. Crosstalk between auxin and ethylene in root elongation has been demonstrated, but interactions between these hormones in root branching are not well characterized. We find that enhanced ethylene synthesis, resulting from the application of low concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), promotes the initiation of lateral root primordia. Treatment with higher doses of ACC strongly inhibits the ability of pericycle cells to initiate new lateral root primordia, but promotes the emergence of existing lateral root primordia: behaviour that is also seen in the eto1 mutation. These effects are correlated with decreased pericycle cell length and increased lateral root primordia cell width. When auxin is applied simultaneously with ACC, ACC is unable to prevent the auxin stimulation of lateral root formation in the root tissues formed prior to ACC exposure. However, in root tissues formed after transfer to ACC, in which elongation is reduced, auxin does not rescue the ethylene inhibition of primordia initiation, but instead increases it by several fold. Mutations that block auxin responses, slr1 and arf7 arf19, render initiation of lateral root primordia insensitive to the promoting effect of low ethylene levels, and mutations that inhibit ethylene-stimulated auxin biosynthesis, wei2 and wei7, reduce the inhibitory effect of higher ethylene levels, consistent with ethylene regulating root branching through interactions with auxin. PMID:18435826

Ivanchenko, Maria G; Muday, Gloria K; Dubrovsky, Joseph G

2008-07-01

369

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. PMID:9748453

Cheng, Hai-Ping; Walker, Graham C.

1998-01-01

370

Novel software for analysis of root gravitropism: comparative response patterns of Arabidopsis wild-type and axr1 seedlings  

NASA Technical Reports Server (NTRS)

In an earlier study (Evans, Ishikawa & Estelle 1994, Planta 194, 215-222) we used a video digitizer system to compare the kinetics of auxin action on root elongation in wild-type seedlings and seedlings of auxin response mutants of Arabidopsis thaliana (L.) Heynh. We have since modified the system software to allow determination of elongation on opposite sides of vertical or gravistimulated roots and to allow continuous measurement of the angle of orientation of sequential subsections of the root during the response. We used this technology to compare the patterns of differential growth that generate curvature in roots of the Columbia ecotype and in the mutants axr1-3, axr1-12 and axr2, which show reduced gravitropic responsiveness and reduced sensitivity to inhibition by auxin. The pattern of differential growth during gravitropism differed in roots of wild-type and axr1 seedlings. In wild-type roots, initial curvature resulted from differential inhibition of elongation in the distal elongation zone (DEZ). This was followed by an acceleration of elongation along the top side of the DEZ. In roots of axr1-3, curvature resulted from differential stimulation of elongation whereas in roots of axr1-12 the response was variable. Roots of axr2 did not exhibit gravitropic curvature. The observation that the pattern of differential growth causing curvature is dramatically altered by a change in sensitivity to auxin is consistent with the classical Cholodny-Went theory of gravitropism which maintains that differential growth patterns induced by gravistimulation are mediated primarily by gravi-induced shifts in auxin distribution. The new technology introduced with this report allows automated determination of stimulus response patterns in the small but experimentally popular roots of Arabidopsis.

Ishikawa, H.; Evans, M. L.

1997-01-01

371

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

372

Mathematica with ROOT  

E-print Network

We present an open-source Mathematica importer for CERN ROOT files. Taking advantage of Mathematica's import/export plug-in mechanism, the importer offers a simple, unified interface that cleanly wraps around its MathLink-based core that links the ROOT libraries with Mathematica. Among other tests for accuracy and efficiency, the importer has also been tested on a large (~5 Gbyte) file structure, D3PD, used by the ATLAS experiment for offline analysis without problems. In addition to describing the installation and usage of the importer, we discuss how the importer may be further improved and customized. A link to the package can be found at: http://library.wolfram.com/infocenter/Articles/7793/ and a related presentation is at: http://cd-docdb.fnal.gov/cgi-bin/DisplayMeeting?conferenceid=522

Ken Hsieh; Thomas G. Throwe; Sebastian White

2011-02-24

373

The root-colonizing endophyte Pirifomospora indica confers drought tolerance in Arabidopsis by stimulating the expression of drought stress-related genes in leaves.  

PubMed

Piriformospora indica is an endophytic fungus that colonizes the roots of many plant species, including Arabidopsis. We exposed 18-day-old Arabidopsis seedlings, which were either cocultivated with the fungus or mock-treated for the last 9 days, to mild drought stress for 84 h. During the first 36 to 48 h, seedlings cocultivated with the fungus continued to grow, while the uncolonized controls did not. This results in a threefold difference in the fresh weight and a more than twofold difference in the chlorophyll content. The photosynthetic efficiency was only slightly reduced in the colonized (F variable/F maximum [Fv/Fm] at t(0 h) = 0.82 and t(36 h) = 0.79) and was severely impaired in the uncolonized (Fv/Fm at t(0 h) = 0.81 and (t)(36 h) = 0.49) seedlings, which also showed symptoms of withering. When seedlings exposed to drought stress for 72 or 84 h were transferred to soil, 10% (72 h) and none (84 h) of uncolonized seedlings reached the flowering stage and produced seeds, while 59% (72 h) and 47% (84 h) of the colonized seedlings flowered and produced seeds. After exposure to drought stress for 3 h, the message levels for RESPONSE TO DEHYDRATION 29A, EARLY RESPONSE TO DEHYDRATION1, ANAC072, DEHYDRATION-RESPONSE ELEMENT BINDING PROTEIN2A, SALT-, AND DROUGHT-INDUCED RING FINGER1, phospholipase Ddelta, CALCINEURIN B-LIKE PROTEIN (CBL)1, CBL-INTERACTING PROTEIN KINASE3, and the histone acetyltransferase (HAT) were upregulated in the leaves of P. indica-colonized seedlings. Uncolonized seedlings responded 3 to 6 h later, and the message levels increased much less. We identified an Arabidopsis ethylmethane-sulfonate mutant that is less resistant to drought stress and in which the stress-related genes were not upregulated in the presence of P. indica. Thus, P. indica confers drought-stress tolerance to Ar