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PubMed1999

Root water flow and growth of aspen (Populus tremuloides) at low root temperatures.

Effects of root zone temperature on growth, shoot water relations, and root water flow were studied in 1-year-old aspen (Populus tremuloides Michx.) seedlings. Seedlings were grown in solution culture and exposed to day/night air temperatures of 22/16 degrees C and solution culture temperatures of 5, 10, or 20 degrees C for 28 days after bud flush. Compared with root growth at 20 degrees C, root growth was completely inhibited at 5 degrees C and inhibited by 97% at 10 degrees C. The 5 and 10 degrees C treatments severely reduced shoot growth, leaf size, and total leaf area. Root water flow was inhibited by the 5 and 10 degrees C treatments. However, when seedlings were grown for 28 days at 5 degrees C and root water flow was measured at 20 degrees C, there was an increase in flow rate. This increase in root water flow was similar in magnitude to the decrease in root water flow observed when seedlings were grown for 28 days at 20 degrees C and root water flow was measured at 5 degrees C. Reduced root water flow of seedlings grown at 5 and 10 degrees C resulted in decreased stomatal conductance, net assimilation, and shoot water potentials. Root water flow was positively correlated with leaf size, total leaf area, shoot length, and new root growth. Transferring seedlings from 5 to 20 degrees C for 24 h significantly increased root water flow, shoot water potential, and net photosynthesis, whereas transferring seedlings from 10 to 20 degrees C resulted in only a slightly increased shoot water potential. Transferring seedlings from 20 to 5 degrees C greatly reduced root water flow, stomatal conductance, and net photosynthesis, whereas shoot water potential decreased only slightly.

Journal Article↗
PubMed2001

The quality of root fillings remaining in mandibular incisors after root-end cavity preparation.

AIM: The aim of this study was to determine the quality of root fillings remaining in mandibular incisors after root-end resection and root-end cavity preparation. METHODOLOGY: Roots of 40 mandibular incisors,12 mm in length, were divided into two groups and instrumented using a balanced force technique and obturated by vertically compacted warm gutta-percha. In one group sealer was used when back-filling the root canal with the Obtura System. The other group was also back-filled with the Obtura System but without sealer. The apical 4 mm of each root filling was removed by root-end resection and root-end cavity preparation. Fluid transport along the 7 mm of remaining root filling was measured. After the leakage test, horizontal sections were cut at a level 3 mm from the apical end of the remaining root filling. The cross sectional area of the canal and gutta-percha was measured using an image analysis program. The quality of the remaining root fillings was also evaluated by calculating the percentage of gutta-percha filled canal area. RESULTS: In total, 27 (67%) out of the 40 roots demonstrated leakage. No significant difference was found between the two groups (P = 0.265). In the cross-sections the bucco-lingual canal diameter was up to 2.6 mm long (mean 1.6 mm). The average percentage of gutta-percha filled canal area was 85.6%. Warm gutta-percha could not obturate areas where debris remained after instrumentation. CONCLUSIONS: The quality of the root fillings in mandibular incisors was poor, probably because the unprepared recesses of oval canals were not clean.

Dental Leakage↗
PubMed1985

Geoperception in primary and lateral roots of Phaseolus vulgaris (Fabaceae). III. A model to explain the differential georesponsiveness of primary and lateral roots.

Half-tipped primary and lateral roots of Phaseolus vulgaris bend toward the side of the root on which the intact half tip remains. Therefore, tips of lateral and primary roots produce growth effectors capable of inducing gravicurvature. The asymmetrical placement of a tip of a lateral root onto a detipped primary root results in the root bending toward the side of the root onto which the tip was placed. That is, the lesser graviresponsiveness of lateral roots as compared with primary roots is not due to the inability of their caps to produce growth inhibitors. The more pronounced graviresponsiveness of primary roots is positively correlated with the presence of columella tissues that are 3.8 times longer, 1.7 times wider, and 10.5 times more voluminous than the columellas of lateral roots. We propose that the lack of graviresponsiveness exhibited by lateral roots is due to the fact that they (i) produce smaller amounts of the inhibitor than primary (i.e., strongly graviresponsive) roots and (ii) are unable to redistribute the inhibitor so as to be able to create a concentration gradient sufficient to induce a pronounced gravitropic response.

Fabaceae↗
PubMed2002

Autoregulation of root nodule formation: signals of both symbiotic partners studied in a split-root system of Vicia sativa subsp. nigra.

Inhibition of root nodule formation on leguminous plants by already induced or existing root nodules is called autoregulation of root nodule formation (AUT). Optimal conditions for AUT were determined using a split-root technique newly developed for Vicia sativa subsp. nigra. Infection of a root A with nodulating Rhizobium leguminosarum bv. viciae bacteria systemically inhibited nodulation of a spatially separated root B inoculated 2 days later with the same bacteria. This treatment gives complete AUT (total absence of nodules on root B). Only partial AUT of root B was obtained by incubation of root A with mitogenic nodulation (Nod) factors or with a noninfective strain producing normal mitogenic Nod factors. Nonmitogenic Nod factors did not evoke AUT. We identified two systemic plant signals induced by Rhizobium bacteria. Signal 1 (at weak buffering) was correlated with sink formation in root A and induced acidification of B-root medium. This signal is induced by treatment of root A with (i) nodulating rhizobia, (ii) mitogenic Nod factors, (iii) nonmitogenic Nod factors, or (iv) the cytokinin zeatin. Signal 2 (at strong buffering) could only be evoked by treatment with nodulating rhizobia or with mitogenic Nod factors. Most probably, this signal represents the specific AUT signal. Induction of complete AUT appears to require actively dividing nodule cells in nodule primordia, nodule meristems, or both of root A.

Culture Media↗
PubMed2001

Root hair initiation is coupled to a highly localized increase of xyloglucan endotransglycosylase action in Arabidopsis roots.

Root hairs are formed by two separate processes: initiation and subsequent tip growth. Root hair initiation is always accompanied by a highly localized increase in xyloglucan endotransglycosylase (XET) action at the site of future bulge formation, where the trichoblast locally loosens its cell wall. This suggests an important role of XET in the first stages of root hair initiation. The tip of growing root hairs is not marked by localized high XET action. Experiments in which root hair initiation was modulated and observations on root hair mutants support this view. The ethylene precursor 1-aminocyclopropane-1-carboxylic acid shifts both root hair initiation and the local increase in XET action toward the root tip. On the other hand, roots treated with the ethylene inhibitor aminoethoxyvinyl-glycine, as well as roots of mutants affected in root hair initiation (rhl1, rhd6-1, and axr2-1) revealed no localized increases of XET action at all and consequently did not initiate root hairs. Disruption of actin and microtubules did not prevent the localized increase in XET action. Also, the temporal and spatial pattern of action as the specific pH dependence suggest that different isoforms of XET act in different processes of root development.

Actins↗
PubMed2001

Role of root hairs and lateral roots in silicon uptake by rice.

The rice plant (Oryza sativa L. cv Oochikara) is known to be a Si accumulator, but the mechanism responsible for the high uptake of Si by the roots is not well understood. We investigated the role of root hairs and lateral roots in the Si uptake using two mutants of rice, one defective in the formation of root hairs (RH2) and another in that of lateral roots (RM109). Uptake experiments with nutrient solution during both a short term (up to 12 h) and relatively long term (26 d) showed that there was no significant difference in Si uptake between RH2 and the wild type (WT), whereas the Si uptake of RM109 was much less than that of WT. The number of silica bodies formed on the third leaf in RH2 was similar to that in WT, but the number of silica bodies in RM109 was only 40% of that in WT, when grown in soil amended with Si under flooded conditions. There was also no difference in the shoot Si concentration between WT and RH2 when grown in soil under upland conditions. Using a multi-compartment transport box, the Si uptake at the root tip (0-1 cm, without lateral roots and root hairs) was found to be similar in WT, RH2, and RM109. However, the Si uptake in the mature zone (1-4 cm from root tip) was significantly lower in RM109 than in WT, whereas no difference was found in Si uptake between WT and RH2. All these results clearly indicate that lateral roots contribute to the Si uptake in rice plant, whereas root hairs do not. Analysis of F(2) populations between RM109 and WT showed that Si uptake was correlated with the presence of lateral roots and that the gene controlling formation of lateral roots and Si uptake is a dominant gene.

Cell Surface Extensions↗
PubMedDate not supplied

Study of root canals and their configuration in buccal roots of maxillary first permanent molar.

The present in-vitro study was undertaken to understand root canals and their configuration in buccal roots of maxillary first permanent molar. Seventy five teeth were studied by the radiographic method and 78 teeth were studied by the decalcification method. Radiographically, in mesiobuccal root, 2 root canals were observed in 81.3% and 18.7% of the specimens in mesiodistal and bucco-lingual direction respectively. In 1.3% of the specimens, 3 root canals were seen in the mesiodistal direction. Radiographically, in distobuccal root, 2 root canals were seen in 9.3% and 1.3% of the specimens in mesiodistal and buccolingual direction respectively. By the decalcification method, 2 root canals were found in mesiobuccal root in 65.4% of the specimens; distobuccal root exhibited 1 canal in 100% of the specimens studied. The configuration (shape) of buccal root canals also varied in both radiological as well as decalcification methods Many specimens exhibited curved canals and in some specimens S-shaped canals were observed. It is concluded from this study that more attention should be directed towards searching for and locating the second root canal in the mesiobuccal root of maxillary first permanent molar.

Dental Pulp Cavity↗
PubMed1993

Water Transport in Onion (Allium cepa L.) Roots (Changes of Axial and Radial Hydraulic Conductivities during Root Development).

The hydraulic architecture of developing onion (Allium cepa L. cv Calypso) roots grown hydroponically was determined by measuring axial and radial hydraulic conductivities (equal to inverse of specific hydraulic resistances). In the roots, Casparian bands and suberin lamellae develop in the endodermis and exodermis (equal to hypodermis). Using the root pressure probe, changes of hydraulic conductivities along the developing roots were analyzed with high resolution. Axial hydraulic conductivity (Lx) was also calculated from stained cross-sections according to Poiseuille's law. Near the base and the tip of the roots, measured and calculated Lx values were similar. However, at distances between 200 and 300 mm from the apex, measured values of Lx were smaller by more than 1 order of magnitude than those calculated, probably because of remaining cross walls between xylem vessel members. During development of root xylem, Lx increased by 3 orders of magnitude. In the apical 30 mm (tip region), axial resistance limited water transport, whereas in basal parts radial resistances (low radial hydraulic conductivity, Lpr) controlled the uptake. Because of the high axial hydraulic resistance in the tip region, this zone appeared to be "hydraulically isolated" from the rest of the root. Changes of the Lpr of the roots were determined by measuring the hydraulic conductance of roots of different length and referring these data to unit surface area. At distances between 30 and 150 mm from the root tip, Lpr was fairly constant (1.4 x 10-7 m s-1 MPa-1). In more basal root zones, Lpr was considerably smaller and varied between roots. The low contribution of basal zones to the overall water uptake indicated an influence of the exodermal Casparian bands and/or suberin lamellae in the endodermis or exodermis, which develop at distances larger than 50 to 60 mm from the root tip.

Journal Article↗
PubMed1996

Root Carbon Dioxide Fixation by Phosphorus-Deficient Lupinus albus (Contribution to Organic Acid Exudation by Proteoid Roots).

When white lupin (Lupinus albus L.) is subjected to P deficiency lateral root development is altered and densely clustered, tertiary lateral roots (proteoid roots) are initiated. These proteoid roots exude large amounts of citrate, which increases P solubilization. In the current study plants were grown with either 1 mM P (+P-treated) or without P (-P-treated). Shoots or roots of intact plants from both P treatments were labeled independently with 14CO2 to compare the relative contribution of C fixed in each with the C exuded from roots as citrate and other organic acids. About 25-fold more acid-stable 14C, primarily in citrate and malate, was recovered in exudates from the roots of -P-treated plants compared with +P-treated plants. The rate of in vivo C fixation in roots was about 4-fold higher in -P-treated plants than in +P-treated plants. Evidence from labeling intact shoots or roots indicates that synthesis of citrate exuded by -P-treated roots is directly related to nonphotosynthetic C fixation in roots. C fixed in roots of -P-treated plants contributed about 25 and 34% of the C exuded as citrate and malate, respectively. Nonphotosynthetic C fixation in white lupin roots is an integral component in the exudation of large amounts of citrate and malate, thus increasing the P available to the plant.

Journal Article↗
PubMed1986

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

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

Allium↗
PubMed1983

Effects of sciatic nerve crush on the L7 spinal roots and dorsal root ganglia in kittens.

The number and size distribution of axons and neurons were examined in the L7 spinal roots and ganglia of kittens 14 to 220 days after early postnatal sciatic nerve crush. The results show that motoraxons in the ventral root as well as axons and perikarya of sensory neurons in the dorsal root remained growth-retarded throughout the examined period. This was most evident in the dorsal root. Both ventral and dorsal roots showed some loss of myelinated axons, but this was only half that previously observed after sciatic nerve resection. Whereas in the dorsal roots and dorsal root ganglia the loss seemed to be nonselective with respect to size, axons in the gamma range were primarily affected in the ventral roots. In the dorsal roots the proportion of unmyelinated axons was comparable with controls but in the ventral roots it was somewhat elevated. In most cases the loss of dorsal root ganglion neurons was relatively greater than the decrease of dorsal root axons.

Animals↗
PubMed1998

Alfalfa (Medicago sativa L.) resistance to the root-lesion nematode, Pratylenchus penetrans: defense-response gene mRNA and isoflavonoid phytoalexin levels in roots.

Alfalfa (Medicago sativa) varieties with antibiosis-based resistance to the root-lesion nematode (Pratylenchus penetrans), a migratory endoparasite of many crops, have been developed by recurrent selection. Individual plants from these varieties that support significantly lower nematode reproduction were identified for molecular and biochemical characterization of defense responses. Before nematode infection, RNA blot analysis revealed 1.3-1.8-fold higher phenylpropanoid pathway mRNA levels in roots of three resistant plants as compared to three susceptible alfalfa plants. The mRNAs encoded the first enzyme in the pathway (phenylalanine ammonia-lyase), the first in the pathway branch for flavonoid biosynthesis (chalcone synthase), a key enzyme in medicarpin biosynthesis (isoflavone reductase) and a key enzyme in the pathway branch for biosynthesis of lignin cell wall precursors (caffeic acid O-methyltransferase). After nematode infection, the mRNAs declined over 48 h in resistant roots but rose in susceptible plants during the first 12 h after-infection and then declined. Acidic beta-1,3-glucanase mRNA levels were initially similar in both root types but accumulated more rapidly in resistant than in susceptible roots after nematode infection. Levels of a class I chitinase mRNA were similar in both root types. Histone H3.2 mRNA levels, initially 1.3-fold higher in resistant roots, declined over 6-12 h to levels found in susceptible roots and remained stable in both root types thereafter. Defense-response gene transcripts in roots of nematode-resistant and susceptible alfalfa plants thus differed both constitutively and in inductive responses to nematode infection. HPLC analysis of isoflavonoid-derived metabolites of the phenylpropanoid pathway revealed similar total constitutive levels, but varying relative proportions and types, in roots of the resistant and susceptible plants. Nematode infection had no effect on isoflavonoid levels. Constitutive levels of the phytoalexin medicarpin were highest in roots of the two most resistant plants. Medicarpin inhibited motility of P. penetrans in vitro.

Acyltransferases↗
PubMed1997

Short-term tissue response to potential root-end filling materials in infected root canals.

The short-term tissue responses to two potential root-end filling materials, a light-cured glass ionomer cement (Vitrebond) and a reinforced zinc oxide-eugenol cement (Kalzinol), were compared with that to amalgam using a previously devised experimental model. In 24 premolar teeth of beagle dogs (47 roots), a collection of endodontic pathogenic bacteria was first inoculated into the root canals to induce periradicular lesions. On each root, an apicoectomy was performed and root-end cavities prepared to receive fillings of each material. The teeth and surrounding jaw were removed after 2 weeks (23 roots) and 1 week (24 roots); they were then prepared for histological examination. The tissue response to amalgam fillings after 2 weeks and 1 week was marked by moderate or severe inflammation on all roots, and extended to < or = 0.5 mm or > 0.5 mm in 15 out of 16 roots. In contrast, after 2 weeks, the majority of roots filled with Kalzinol showed little or moderate inflammation, while the tissue response to Vitrebond was the best of the three materials, and was also the least extensive. After 1 week, the overall best tissue response was with Vitrebond, followed by Kalzinol. The differences between materials for both time periods with either none or few inflammatory cells when compared with that with either moderate or severe inflammation were not statistically significant (P < 0.02). However, the differences between materials for both time periods with no inflammation or inflammation extending < 0.2 mm when compared with that with inflammation extending > 0.2 mm (< or = 0.5 mm or > 0.5 mm) were statistically significant (P < 0.01). Apart from amalgam, in which healing was marked by the persistence of a localized focus of inflammation adjacent to the root-end filling, even though there were intersample variations, there was little overall difference in the temporal and qualitative healing response to Vitrebond and Kalzinol. Both Vitrebond and Kalzinol have potential as root-end filling materials, as the tissue response was considerably more favourable than that to amalgam even in the short-term.

Animals↗
PubMed1996

The effects of mechanical compression and hypoxia on nerve root and dorsal root ganglia. An analysis of ectopic firing using an in vitro model.

STUDY DESIGN: This study analyzed in vitro experiments of ectopic firing evoked by mechanical compression or hypoxia of canine lumbar dorsal roots with dorsal root ganglia using an in vitro model. OBJECTIVES: The results were correlated to understand the pathophysiology of radiculopathy, which manifests abnormal sensation and pain. SUMMARY OF BACKGROUND DATA: It has been speculated that blood flow in the nerve root and mechanical compression play major roles in the production of radiculopathy symptoms. However, no precise experimental studies have been conducted on the relationship between these factors and the development of ectopic firing. METHODS: Canine lumbar dorsal roots with dorsal root ganglia were immersed in an oxygenated artificial cerebrospinal fluid, and activity of the nerve root was recorded using bipolar platinum electrodes. Using this model, the effects of quantitative mechanical compression and hypoxia on the ectopic firing were analyzed. RESULTS: When compression was applied, mechanical thresholds for eliciting firing were much lower in dorsal root ganglia than in dorsal roots, and the firing lasted for a longer period in dorsal root ganglia. Under hypoxia, dorsal root ganglia showed firing, and their thresholds from mechanical stimuli decreased significantly. In dorsal roots, impulse propagation was not affected, whereas firing was seen under the hypoxic condition. CONCLUSION: Dorsal root ganglia are highly sensitive to mechanical compression and hypoxia and closely related to abnormal sensations and pain in radiculopathy.

Action Potentials↗
PubMed1998

Phospholipase A2 sensitivity of the dorsal root and dorsal root ganglion.

STUDY DESIGN: This study was designed to characterize the effects of phospholipase A2 on the neural response of dorsal root and dorsal root ganglion in the anesthetized New Zealand White rabbit. OBJECTIVES: To examine the effects of phospholipase A2 on the neural response of somatosensory neurons at the dorsal root ganglion level. SUMMARY OF BACKGROUND DATA: Phospholipase A2 may be an irritating component of disc tissue that is present in high concentration in painful herniated discs, in synovial fluids, and in sera of rheumatoid arthritis patients. Phospholipase A2 is inflammatory; however, its effects on dorsal roots and dorsal root ganglion response have never been demonstrated. METHODS: Surgically isolated dorsal roots and dorsal root ganglia from New Zealand White rabbits were investigated by electrophysiologic techniques. Phospholipase A2 doses ranging from 100 to 400 U were applied on the mechanically sensitive segments of the dorsal root ganglia, and responses to varying doses were evaluated in relation to elapsed time. RESULTS: The application of phospholipase A2 on the dorsal root ganglion resulted in possible neurotoxicity at doses more than 375 U, with no significant effect at lower doses except for recruitment of "silent units" at doses ranging from 200 to 340 U. CONCLUSIONS: Phospholipase A2 doses comparable to serum concentrations in human rheumatoid arthritis appeared to be neurotoxic when applied to dorsal root ganglia. At lower doses, silent units become activated that were not active before the phospholipase A2 application. These results suggest that dorsal roots and dorsal root ganglion may be impaired by phospholipase A2, leading to sciatica and low back pain.

Analysis of Variance↗
PubMed1996

pH changes at the surface of root dentin when using root canal sealers containing calcium hydroxide.

The purpose of this study was to investigate long-term pH changes in cavities prepared in root surface dentin of extracted teeth after obturation of the root canal with gutta-percha and a variety of sealers containing calcium hydroxide. After cleaning and shaping, root canals in 50 recently extracted, human single-rooted teeth were divided into five groups. Each of four groups was obturated with gutta-percha and either Sealapex, Sealer 26, Apexit, or CRCS, all of which contain calcium hydroxide. The remaining group served as the control and was not obturated with gutta-percha or sealer. Cavities were prepared in the facial surface of the roots in the cervical and middle regions. The pH was measured in these dentinal cavities at the initiation of the experiment, and 3, 7, 14, 21, 28, 45, 60, 90, and 120 days after obturation. Results indicate that the pH at the surface of the root does not become alkaline when calcium hydroxide cements are used as root canal sealers. Regardless of the sealer used, the observed pattern of pH change was not different from that seen in the control group of roots that were not treated with sealer. It is concluded that calcium hydroxide-containing cements, although suitable for use as root canal sealants, do not produce an alkaline pH at the root surface. If such a pH change is related to treatment of root resorption, these sealants do not contribute to this treatment.

Bismuth↗
PubMed2001

Assessment of root resorption and root shape: periapical vs panoramic films.

A radiographic examination is an essential part of the diagnostic process in orthodontics. However, what radiographs are needed to properly evaluate root shape and position? Most clinicians order panoramic or periapical radiographs in addition to the cephalometric radiograph. The purpose of this study was to find out whether one type of film is more accurate than the other in the pretreatment evaluation of root shape and the posttreatment computation of apical root resorption. Pretreatment and posttreatment panoramic films and full-mouth periapical films from 42 patients who completed fixed orthodontic treatment were assessed for tooth length and root shape. Panoramic films showed significantly greater average apicaL root resorption than periapical films for the 743 teeth surveyed. The greatest differences were found in the lower incisors, the least in the maxillary incisors. Classification of root shape was significantly different between the 2 types of radiographs. Root dilacerations and other abnormal shapes, clearly visible on periapical films, often appeared normal on panoramic films. The findings strongly suggest that root shape is much harder to assess on panoramic films. We conclude that, in cases where the apices are obscured or other factors are present that might suggest higher risk for root resorption or vertical bone loss, periapical films should be ordered. The use of panoramic films to measure pre- and posttreatment root resorption may overestimate the amount of root loss by 20% or more.

Adolescent↗
PubMed1991

Lateral root initiation in Marsilea quadrifolia. I. Origin and histogensis of lateral roots.

In Marsilea quadrifolia, lateral roots arise from modified single cells of the endodermis located opposite the protoxylem poles within the meristematic region of the parent root. The initial cell divides in four specific planes to establish a five-celled lateral root primordium, with a tetrahedral apical cell in the centre and the oldest merophytes and the root cap along the sides. The cells of the merophyte divide in a precise pattern to give rise to the cells of the cortex, endodermis, pericycle, and vascular tissues of the emerging lateral root. Although the construction of the parent root is more complicated than that of lateral roots, patterns of cell division and tissue formation are similar in both types of roots, with the various tissues being arranged in similar positions in relation to the central axis. Vascular connection between the lateral root primordium and the parent root is derived from the pericycle cells lying between the former and the protoxylem members of the latter. It is proposed that the central axis of the root is not only a geometric centre, but also a physiological centre which determines the fate of the different cell types.

Cell Differentiation↗