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At least 253 records · Page 14Linked to original sources
PubMed2005

Root-ABA1, a major constitutive QTL, affects maize root architecture and leaf ABA concentration at different water regimes.

Near-isogenic hybrids (NIHs), developed from crossing maize (Zea mays L.) backcross-derived lines (BDLs) differing for the parental alleles at a major QTL for leaf ABA concentration (L-ABA), were field-tested for 2 years under well-watered and water-stressed conditions. Differences among NIHs for L-ABA and other morpho-physiological traits were not affected by water regimes. On average, the QTL allele for high L-ABA markedly reduced stomatal conductance and root lodging. To elucidate the effects of the QTL on root architecture and L-ABA, root traits of two pairs of BDLs were measured in plants grown in soil columns at three water regimes. Differences among BDLs were not affected by water regimes. Across water regimes, the QTL confirmed its effect on L-ABA and showed a concurrent effect on root angle, branching, number, diameter, and dry weight. Based on these results, it is concluded that the QTL affects root lodging through a constitutive effect on root architecture. In addition, there is speculation that the QTL effects on root traits and L-ABA are probably due to pleiotropy rather than linkage and a model is proposed in which the QTL has a direct effect on root architecture, while indirectly affecting L-ABA.

Abscisic Acid↗
PubMed2006

Root-ABA1 QTL affects root lodging, grain yield, and other agronomic traits in maize grown under well-watered and water-stressed conditions.

A major QTL affecting root traits and leaf ABA concentration was identified in maize (Zea mays L.) and named root-ABA1. For this QTL, back-cross-derived lines (BDLs) homozygous either for the (+) or for the (-) allele increasing or decreasing, respectively, root size and leaf ABA concentration, were developed. This study was conducted to evaluate the QTL effects in various genetic backgrounds and at different water regimes. The (+/+) and (-/-) BDLs were crossed with five or 13 inbred tester lines of different origin, thus producing two sets of test-crosses that were evaluated in Italy and China, respectively. Testing was conducted under both well-watered and water-stressed conditions. In Italy, the test-crosses derived from (+/+) BDLs, as compared with those derived from (-/-) BDLs, showed, across both water regimes, higher leaf ABA concentration (on average 384 versus 351 ng g(-1) DW) and lower root lodging (28.0 versus 52.5%), and lower grain yield under water-stressed conditions (4.88 versus 6.27 Mg ha(-1)). In China, where root lodging did not occur, the test-crosses derived from (+/+) BDLs were less productive at both water regimes (on average, 6.83 versus 7.49 Mg ha(-1)). The lower grain yield of the test-crosses derived from (+/+) BDLs was due to a lower number of ears per plant and to lower kernel weight. The results indicate that the (+) root-ABA1 allele confers not only a consistently lower susceptibility to root lodging but also a lower grain yield, especially when root lodging does not occur.

Abscisic Acid↗
PubMed2005

Reactive oxygen species and root hairs in Arabidopsis root response to nitrogen, phosphorus and potassium deficiency.

Plant root sensing and adaptation to changes in the nutrient status of soils is vital for long-term productivity and growth. Reactive oxygen species (ROS) have been shown to play a role in root response to potassium deprivation. To determine the role of ROS in plant response to nitrogen and phosphorus deficiency, studies were conducted using wild-type Arabidopsis and several root hair mutants. The expression of several nutrient-responsive genes was determined by Northern blot, and ROS were quantified and localized in roots. The monitored genes varied in intensity and timing of expression depending on which nutrient was deficient. In response to nutrient deprivation, ROS concentrations increased in specific regions of the Arabidopsis root. Changes in ROS localization in Arabidopsis and in a set of root hair mutants suggest that the root hair cells are important for response to nitrogen and potassium. In contrast, the response to phosphorus deprivation occurs in the cortex where an increase in ROS was measured. Based on these results, we put forward the hypothesis that root hair cells in Arabidopsis contain a sensing system for nitrogen and potassium deprivation.

Arabidopsis↗
PubMed2005

Transgenic proteoid roots of white lupin: a vehicle for characterizing and silencing root genes involved in adaptation to P stress.

White lupin (Lupinus albus L.) has become an illuminating model for the study of plant adaptation to phosphorus (P) deficiency. It adapts to -P stress with a highly coordinated modification of root development and biochemistry resulting in short, densely clustered secondary roots called proteoid (or cluster) roots. In order to characterize genes involved in proteoid root formation and function in a homologous system, we have developed an Agrobacterium rhizogenes-based transformation system for white lupin roots that allows rapid analysis of reporter genes as well as RNA interference (RNA(i))-based gene silencing. We used this system to characterize a lupin multidrug and toxin efflux (Lupinus albus MULTIDRUG AND TOXIN EFFLUX, LaMATE) gene previously shown to have enhanced expression under -P stress. Here, we show that LaMATE had high expression in proteoid roots not only under -P, but also under -Fe, -N, -Mn and +Al stress. A portion containing the putative LaMATE promoter was fused to GUS and enhanced green fluorescence protein (EGFP) reporter genes, and a translational LaMATE::EGFP fusion was constructed under control of the LaMATE promoter. The LaMATE promoter directed P-dependent GUS and EGFP expression to proteoid roots. Confocal microscopy in white lupin and Arabidopsis point to the plasma membrane as the likely location of the LaMATE protein. LaMATE displayed homology to FRD3 in Arabidopsis, but did not complement an Arabidopsis ferric reductase defective 3 (FRD3) mutant. RNA(i)-based gene silencing was shown to effectively reduce LaMATE expression in transformed white lupin roots. LaMATE RNAi-silenced plants displayed an about 20% reduction in dry weight.

Adaptation, Physiological↗
PubMed1980

Assessing root caries in populations: the evolution of the root caries index.

This paper traces the history of the epidemiologic assessment of root caries over the past 30 years. This history clearly points out that a critical junction has been reached between the state-of-the art for the reporting of root caries and the demand placed on research and service components of the oral health system. If progress is to be made, it is imperative that a uniform reporting method for root caries be adopted. This paper introduces the Root Caries Index (RCI) as an index that should prove to be a feasible and utilitarian method for reporting root caries data in descriptive and analytic epidemiologic studies as well as assessing the results of preventive and treatment agents, clinical trials. The Root Caries Index represents, in the evolution of a root caries measurement method, a refinement of the delineation of the true intraoral "population at risk" to the disease process. The resulting index is a true attack rate for supragingival root caries lesions. This development should permit more meaningful comparison of populations, clearer interpretations regarding risk factors, and more precise assessment of preventive and treatment agents.

Adolescent↗
PubMed1988

Improvement of the caries resistance of human dental roots by a two-step conversion of the root mineral into fluoridated hydroxylapatite.

Roots of extracted human molars were treated for both 10 and 30 min with a saturated solution of dicalcium phosphate dihydrate (DCPD) of pH 2.4 and subsequently with a 5.3 mmol.L-1 solution of sodium fluoride of pH 7.0. The objective of these combined treatments was to convert the highly-soluble root mineral into the less-soluble fluoridated hydroxylapatite, with DCPD as an intermediate, to improve caries resistance. The mineral content of the surface layer was not affected in a significant way. Roots treated in this way were subjected to 50 mmol.L-1 acetate buffer solutions of pH 5.5 and with pIOHA-values of 112, 116, and 122. The proportional reduction of the rate of demineralization (Vdem) of similarly treated roots subjected to buffer solutions of pIOHA 112 and 116 appeared to be equal initially. Since fluoridated hydroxylapatite is insoluble under these conditions, these findings are in agreement with expectations. The reduction of V dem amounted to about 45 and 70% for roots treated for 10 and 30 min, respectively. When roots were treated for 10 and 30 min and then exposed to buffer solutions with a pIOHA 122, reductions of V dem of about 30 and 55%, respectively, were found. Conversion of the root mineral into fluoridated hydroxylapatite can eliminate, in principle, the existing difference in caries susceptibility of the root and of the dental enamel.

Calcium Phosphates↗
PubMed1991

Effects of fluoride and chlorhexidine on the microflora of dental root surfaces and progression of root-surface caries.

The effects of fluoride and chlorhexidine varnishes on the microflora of dental root surfaces and on the progression of root-surface caries were studied. Forty-four patients, surgically treated for advanced periodontal disease, were distributed at random among three groups. All patients received a standardized preventive treatment. Furthermore, the dentition of the patients in the two experimental groups was treated, at three-month intervals, with chlorhexidine and fluoride varnish, respectively. Patients in the control group received no additional treatment. In the experimental groups, plaque samples were collected from selected sound and carious root surfaces at baseline and at three, six, and nine months after the onset of the study. The presence of root-surface caries was scored at baseline and after one year. In addition, the texture, depth, and color of the root-surface lesions were monitored. Mutans streptococci on root surfaces were suppressed significantly (p less than 0.05) during the whole experimental period in the chlorhexidine varnish group, but not in the fluoride varnish group. A non-significant increase in the number of Actinomyces viscosus/naeslundii was noted after treatment with chlorhexidine and fluoride varnish. The increase in the number of decayed and filled root surfaces after one year was significantly lower in the experimental groups than in the control group. After treatment with chlorhexidine varnish, significantly more initial root-surface lesions had hardened than in the other groups.

Actinomyces↗
PubMedDate not supplied

Enhanced phenanthrene biodegradation in soil by slender oat root exudates and root debris.

To investigate the mechanisms by which slender oat (Avena barbata Pott ex Link) enhances phenanthrene biodegradation, we analyzed the impacts of root exudates and root debris on phenanthrene biodegradation and degrader community dynamics. Accelerated phenanthrene biodegradation rates occurred in soils amended with slender oat root exudates as well as combined root debris + root exudate as compared with unamended controls. Root exudates significantly enhanced phenanthrene biodegradation in rhizosphere soils, either by increasing contaminant bioavailability and/or increasing microbial population size and activity. A modified most probable number (MPN) method was used to determine quantitative shifts in heterotrophic and phenanthrene degrader communities. During the first 4 to 6 d of treatment, heterotrophic populations increased in all amended soils. Both root debris-amended and exudate-amended soil then maintained larger phenanthrene degrader populations than in control soils later in the experiment after much of the phenanthrene had been utilized. Thus, root amendments had a greater impact over time on phenanthrene degraders than heterotrophs resulting in selective maintenance of degrader populations in amended soils compared with controls.

Avena↗
PubMedDate not supplied

[Initial stages of interaction of Azospirillum brasilense bacteria with wheat germ roots: adsorption, deformation of root hairs].

The initial stages of colonization of wheat roots by cells of Azospirillum brasilense strains 75 and 80 isolated from soils of the Saratov oblast were studied. The adsorption of azospirilla on root hairs of soft spring wheats rapidly increased in the first hours of incubation, going then to a plateau phase. Within the first 15 h of incubation, exponential-phase cells were adsorbed more intensively than stationary-phase cells. Conversely, stationary-phase cells were adsorbed more intensively than exponential-phase cells, if the period of azospirilla incubation with the wheat roots was extended. As the time of incubation increased, the attachment of azospirilla to the wheat roots became stronger. The effect of cell attachment to root hairs was strain-dependent; the number of adsorbed cells of a given strain of azospirilla was greater in the case of host wheat cultivars. The deformation of wheat root hairs was affected by the polysaccharide-containing complexes isolated from the capsular material of azospirilla. The suggestion is made that common receptor systems are involved in the adsorption of azospirilla on roots and in root hair deformation.

Azospirillum brasilense↗
PubMedDate not supplied

[Ethylene-induced activation of xylanase in adventitious roots of maize as a response to the stress effect of root submersion].

Submersion of roots of ten-day-old maize (Zea mays L.) seedlings was accompanied by a decrease in pO2 and an increase in pCO2 of the medium adjacent to roots. These changes stimulated ethylene evolution in intact plants. Enhanced biosynthesis of ethylene was accompanied by xylanase activation in adventitious roots. As a result, an enhanced formation of aerenchyma was observed in the cortex of adventitious roots. Therefore, these processes resulted in the development of a ventilation system by which O2 can reach the root system exposed to hypoxia. The volume of aerenchyma was assessed by the volume of gas cavities (porosity). In contrast to the main root, the growth of adventitious roots was not inhibited under these conditions. Enlargement of the stem base and increase in the number of aerenchymatous adventitious roots facilitated the oxygen supply to submerged organs of plants.

Adaptation, Physiological↗
PubMedDate not supplied

[Genetically transformed plant roots as a model for studying specific metabolism and symbiotic contacts of the root system].

Genetic transformation of plants mediated by Ri plasmid of Agrobacterium rhizogenes occupies a special place in plant cell engineering, since this technique based on a natural phenomenon allows cultivation of separately growing roots on hormone-free media. Application of wild-type unmodified agrobacterial strains allows us to obtain root cultures capable of long-term growth in vitro due to an increased sensitivity of the cells to auxins while other biochemical properties remain unaltered. A collection of pRi T-DNA transformed roots of certain dicotyledons was constructed; some strains of it are used to study synthesis of secondary metabolites in root cells. The in vitro cultivated roots could synthesize root-specific metabolites, which allows their large-scale application for biotechnological production of ecologically pure crude drugs. Cocultivation of pRi T-DNA transformed roots with arbuscular mycorrhizal fungi makes possible vital study of all stages of obligate symbiont development and interaction with plant roots. Mixed axenic culture of AM fungi and pRi T-DNA transformed plants can be used to construct a collection of the most valuable endomycorrhizal fungal species and to produce considerable quantities of homogeneous fungal inoculums.

Coculture Techniques↗
PubMed2005

[Allelopathy of root exudates from two genotypes soybeans on root pathogenic fungi].

With biological simulation experiment and chemical analysis, this paper studied the allelopathy of carbohydrates, amino acids and organic acids in the root exudates from two genotypes soybeans (9536 and Jilin 30) on the pathogenic fungi of root rot. The results showed that the water soluble carbohydrates in the root exudates from test soybeans significantly promoted the growth of Fusarium oxysporium and Fusarium semitectum at low concentrations and inhibited their growth at high concentrations, but had no evident influence on Gliocladium roseum. The water soluble amino acids from the root exudates demonstrated different actions, i. e., at middle and high concentrations, those from 9536 significantly inhibited the growth of Fusarium oxysporium, Fusarium semitectum and Gliocladium roseum, while those from Jilin 30 mostly promoted their growth. The organic acids from the root exudates of 9536 and Jilin 30 significantly inhibited the growth of Fusarium oxysporium, Fusarium semitectum and Gliocladium roseum. It's suggested that there existed interactions between the root exudates of the two genotypes soybeans and the pathogenic fungi of root rot. Different genotypes of soybean may have different allelopathy on pathogenic fungi of root rot.

Fusarium↗
PubMed2005

[Root system hydraulic conductivity of different genotype maize and its relationship with root anatomy].

Under solution culture condition and by using pressure chamber techniques, this paper studied the difference of root system hydraulic conductivity (Lpr) of different genotype maize at the level of individual root, and its relationship with root anatomy. The results showed that the Lpr of root system was different with different genotype, and there existed heterosis in F, generation. Under normal culture condition, the root with wider vessels had higher Lpr and drought resistance; while under water deficit, there was a significantly negative correlation between the width of root vessel and the Lpr and drought resistance. Under both normal and deficient water supply, there was a negative correlation between the ratio of cortex to root diameter and the Lpr and drought resistance, suggesting that root cortex was the placement with the greatest resistance to the liquid water flow in

Genotype↗
PubMedDate not supplied

Root canal morphology of the mesiobuccal root in maxillary first molars of a Jordanian population.

This in vitro study investigated the presence of second (MB2) root canals and the number of apical foramina found in mesiobuccal roots of the permanent maxillary first molars; in addition, the study evaluated the effectiveness of magnification to detect MB2 canals. One hundred extracted maxillary first molars were collected from Jordanian patients. The number of roots (as well as their morphology) was investigated. The number of canal orifices in mesiobuccal root was assessed, with and without magnification, and findings were compared. The number of apical foramina and the distance between mesiobuccal and second canal orifices were investigated under magnification. Of the 97 specimens that were subject to additional investigation, all teeth had three separated roots, except for three specimens that had either mesiobuccal or distobuccal roots fused with the palatal root. The number of MB2 canals that were detected increased from 55 (56.7%) to 61 (62.9%) teeth when magnification was used. Within the limits of this in vitro study, it was concluded that the Jordanian population had a high percentage of MB2 canals in the mesial buccal roots. Moreover, the use of clinically used magnifying devices increased the number of MB2 canals detected.

Dental Pulp Cavity↗
PubMed1990

[Coronal repositioning of root fragment by root elongation with a titanium endodontic implant].

Teeth with deep transverse or oblique root fractures can nowadays be preserved by intra-alveolar transplantation. This method, however, has its limitation: The apical root fragment must not be too short in proportion to the crown length. This report describes a method to retain even very short roots. 14 roots have been carefully extracted. Then, the following treatment has been performed extraorally: Apectomy, lengthening of the root with a common titanium root screw and replantation of the root in an extruded position which allowed to carry out correct root filling and crown reconstruction. After an average observation period of 19 months 11 cases out of 14, i.e. 79%, were successful according to the criteria stated by Kristersson and Kvint. If the long-term results turn out as promising as the short-term findings, the concept might well be extended to other indications. One example is to stimulate the growth of a genuine periodontal "re-attachment" in intrabony pockets by extruding viable periodontal membrane areas to a more coronal level.

Adult↗
PubMed1978

Root formation in ectopically transplanted teeth of the frog rana pipiens. II. Comparative aspects of the root tissues.

In the second part of an experimental study of the behavior and fate of the roots of ectopically transplanted frog teeth the comparative aspects of the tooth root and its tissue composition were examined. Experimental results showed that the root or pedicel area of the frog tooth was an intrinsic part of the tooth. The tooth was capable of growth to normal size and shape with or without the presence of underlying bone. When compared with existing descriptive exidence and analysis it was determined that the best terminology for the amphibian root tissues would be dentin right up to the point of attachment where cellular basal bone is seen. This is because it is an intrinsic part of the tooth, if formed on the pulpal side of the root sheath, and is formed by odontoblasts. Because of the above observations, the original Hertwig's epithelial root sheath appeared both homologous and analogous with the mammalian sheath, but since all the root tissues were under this sheath, no tissues homologous to any of the paradental tissues of cementum, periodontal ligament, or alveolar bone could be found except when the root sheath injury resulted in induction of an acellular tissue upon the outer surface of dentin.

Animals↗
PubMed1997

Root canals in two-rooted maxillary second molars.

The aim of this study was to register the root canal number, root canal position, and root canal cross-section in human two-rooted, permanent maxillary second molars. One hundred and fifty-nine such teeth extracted in Denmark were cross-sectioned at the mid-root level and apically in accordance with precise guidelines. The observations were made in a stereomicroscope, corresponding to the above-mentioned section levels. At mid-root there were two canals present in 11% of the teeth examined; the canals were located mesially and distofacially, mesiofacially and distally, or facially and lingually. Three canals positioned mesiofacially, distofacially, and lingually were observed in 89% of the teeth. At the same level 62% of the canal cross-sections were noncircular, some being, for instance, C-shaped, whereas 38% of the cross-sections were circular. Apically, two canals were found, representing 19% of the teeth, with the canal position as at mid-root; 81% of the teeth were three-canaled with the same canal position as at mid-root. At the apical level 60% of the canal cross-sections were noncircular, whereas 40% of the cross-sections were circular.

Anatomy, Cross-Sectional↗
PubMed1998

Mandibular first and second molar. The variability of roots and root canal system.

The root and canal anatomy of mandibular first and second molars has normally recurring features, as well as a great number of atypias. Normally mandibular first and second molars have two roots, one is mesial and the other is distal, and at least three main canals. The roots of the second molar can change from one to three, the first molar can have also four roots; the canals can change from three to even six. The conventional root canal anatomy indicates the location of the initial access. The knowledge of both the normal and abnormal anatomy of molars shows the parameters under which root canal therapy is to be executed and can directly modify the probability of success. This is the reason why endodontists must be familiar with all abnormalities as well as their percentage. We present a review of the modern literature about the event of aberrances with references to the number and morphology in mandibular first and second molar root and root canals.

Dental Pulp Cavity↗