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PubMed1990

[Friction sound as an objective sign of completion of root planing].

Root planing is one of the most important procedures in periodontal treatment. However, there are no objective clinical signs to indicate completion of this procedure. The purpose of this study was to examine the friction sound produced by curettes and root surfaces during root planing and to test the possibility of utilizing the sound changes as an objective parameter for evaluating completion of the procedure. The study consisted of a clinical and laboratory experiment. Seven periodontally diseased teeth were utilized in the clinical trial. During scaling and root planing with the Gracey curette, the friction sound was clinically analyzed with a sound spectrograph. The root surface, in situ, was observed by scanning electron microscopy (SEM) with the replica technique. Twenty-one periodontally diseased teeth were used in the laboratory study. Root planed surfaces were classified as pre-root planed and post-root planed according to their friction sounds during root planing. Each surface was examined by the following methods: 1) measuring root surface roughness 2) SEM observations 3) determination of number of adherent cells by the cultured fibroblast technique. As a result, post-root planed surfaces were well root planed as evaluated by SEM observations and the profilometer. Similarly, adherent cell counts were increased on post-root planed surfaces. These results indicated the possible usefulness of friction sound analysis to judge the completion of root planing.

Cell Adhesion↗
PubMed1985

Unmyelinated fibers in the cervical and lumbar ventral roots of the cat.

Ventral spinal roots at all spinal levels in humans contain many unmyelinated axons, as do all spinal roots of the cat which have been examined. Rats, however, have fewer unmyelinated fibers in cervical and certain lumbar ventral roots. To determine if unmyelinated fibers are distributed uniformly in ventral roots of the cat, cervical and lumbar ventral roots were examined by light and electron microscopy, and axons were counted. Lesions were made to determine the origin of unmyelinated fibers in ventral root L6. From 5 to 15% of the axons in cervical ventral roots are unmyelinated. This distribution of unmyelinated fibers in the cat is similar to the distribution in humans, although the cervical ventral roots of the cat contain relatively fewer unmyelinated fibers than the cervical ventral roots of humans. Approximately 24% of the axons in ventral root L6 are unmyelinated. More than 90% of these axons degenerate proximal to, but not distal to, a ventral rhizotomy and ipsilateral to a dorsal root ganglionectomy. Thus, most unmyelinated axons in ventral root L6 appear to rise from dorsal root ganglion cells. Much variation in the number and percent of unmyelinated axons in ventral roots at the same spinal level exists between individual cats and between opposite sides of the same cat.

Animals↗
PubMed1996

The configuration of the seminal roots of Triticum aestivum L. (Poaceae).

The seminal root system of wheat (Triticum aestivum L.) is composed of the primary seminal root, the first pair of seminal roots, and the second pair of seminal roots, which are known to grow in different directions. The direction of root growth, which can be expressed by theta (the angle between the root and the plumb line) and phi (the angle between the root and a vertical plane including the primary seminal root), was studied with special attention to the latter. It was measured on seedlings grown in a small hemispherical soil-filled mesh basket. There were varietal differences in the phi of the first pair of roots (phi f) and in the phi of the second pair of roots (phi s). phi f and phi s were significantly correlated. The mean distance (MD), a measure to evaluate the efficiency of root spacing, was correlated with the difference between phi f and phi s. Neither experimentally applied low soil water potential nor the excision of the primary seminal root affected phi. When the grain was sown vertically with the tip of the embryo pointing downwards, it was found that the growth movement into a direction different from the plumb line and phi s was greatly modified. It is suggested that certain internal mechanisms, possibly involving gravitropic reactions, are operating to control the direction of root growth. The significance of root growth direction at the seedling stage is discussed.

Gravitropism↗
PubMed2004

Aerenchyma formation and porosity in root of a mangrove plant, Sonneratia alba (Lythraceae).

Aerenchyma gas spaces are important for plants that grow in flooded and anaerobic sites or habitats, because these gas spaces provide an internal pathway for oxygen transport. The objective of this study is to characterize the development of aerenchyma gas spaces and observe the porosity in roots of Sonneratia alba. Tissue at different developmental stages was collected from four root types, i.e. cable root, pneumatophore, feeding root and anchor root, of S. alba. In S. alba, gas space is schizogenously produced in all root types, and increases in volume from the root meristem to mature root tissues. The aerenchyma formation takes place immediately, or 3-5 mm behind the root apex. At first, cortical cells are relatively round in cross sections (near the root apex); they then become two kinds of cells, rounded and armed, which combine together, forming intercellular spaces behind the root apex. The average dimensions of cortical cells increased more than 1.3 times in the vertical direction and over 3.3 times in the horizontal direction. At maturity, aerenchyma gas spaces are long tuberous structures without diaphragms and with numerous small pores on the lateral walls. Within the aerenchyma, many sclereids grow intrusively. Root porosity in all root types ranged from 0-60%. Pneumatophores and cable roots had the highest aerenchyma area (50-60%).

Lythraceae↗
PubMed2004

Expression of alpha-expansin genes during root acclimations to O2 deficiency in Rumex palustris.

Thirteen alpha-expansin genes were isolated from Rumex palustris , adding to the six already documented for this species. Five alpha-expansin genes were selected for expression studies in various organs/tissues of R. palustris , with a focus on roots exposed to aerated or O2)-deficient conditions, using real-time RT-PCR. Several cases of differential expression of alpha-expansin genes in the various root types of R. palustris were documented, and the identity of the dominant transcript differed between root types (i.e., tap root vs. lateral roots vs. adventitious roots). Several genes were expressed differentially in response to low O2. In situ hybridizations showed expansin mRNA expression in the oldest region of the tap root was localized to cells near the vascular cambium; this being the first report of expansin expression associated with secondary growth in roots. In situ hybridization also showed abundant expression of expansin mRNA in the most apical 1 mm of adventitious roots. Such early expression of expansin mRNA in cells soon after being produced by the root apex presumably enables cell wall loosening in the elongation zone of roots. In addition, expression of some expansin mRNAs increased in 'mature zones' of roots; these expansins might be involved in root hair formation or in formation of lateral root primordia. The present findings support the notion that large gene families of alpha-expansins enable flexibility in expression for various organs and tissues as a normal part of plant development, as well as in response to abiotic stress.

Acclimatization↗
PubMed1988

Proportion and location of spinal neurons receiving ventral root afferent inputs in the cat.

Spinal neurons receiving ventral root afferent inputs were investigated in anesthetized and paralyzed cats. We were concerned with the afferent fibers in the ventral root that travel distally and then enter the spinal cord through the dorsal root. The questions to be answered included the proportion and distribution of spinal neurons receiving ventral root afferent inputs and their peripheral input characteristics. The 1.7 ventral root was cut near the spinal cord and the distal stump was stimulated while making a systematic search for neurons in the entire gray matter of the ipsilateral spinal cord that responded to the stimulation. The following conclusions were made: (i) the afferent fibers in the cat ventral root enter the spinal cord through the dorsal root and evoke a variety of responses (excitation, inhibition, or mixed) in a large proportion of spinal neurons (about 20%): (ii) these responses seem to be mediated largely by spinal mechanisms: (iii) spinal neurons receiving ventral root afferent inputs are situated in a wide region of the ventral spinal cord: (iv) ventral root fibers in a single root enter the spinal cord and exert their responses over a large region of the spinal cord (at least two spinal segments rostrally and caudally): (v) some of the spinal neurons that responded to ventral root stimulation were found to be ascending tract cells, suggesting that ventral root afferent inputs can reach supraspinal structures: (vi) ventral root afferent fibers converge onto spinal neurons that have a variety of peripheral receptive field characteristics: and (vii) with some exceptions, most neurons receiving ventral root inputs were excited best by mechanical and/or thermal noxious stimuli applied to the periphery.

Afferent Pathways↗
PubMed1989

Nerve fibre regeneration across the PNS-CNS interface at the root-spinal cord junction.

Root-spinal cord regeneration was investigated in immature and adult rats. The elongation in the dorsal root of regrowing dorsal root axons, rerouted ventral root nerve fibres (cholinergic neurons) or hypogastric nerve fibres (catecholaminergic neurons) is impeded as they meet the astrocyte dominated CNS tissue of the root. The establishment of synaptoid nerve terminals as the regrowing axons encounter astrocytes indicates a mechanism for growth inhibition other than a physical impediment in the CNS environment. The glial cells of the CNS segment in the root are influenced by the type of regenerating nerve fibres in terms of maintenance, multiplication and phenotypic expression. After a dorsal root lesion in the neonatal rat several root axons may reinnervate the spinal cord. In these rats, the normal establishment of a CNS root segment has been disrupted and the PNS-CNS border is situated central to the root-spinal cord junction. Implantation of cut dorsal roots into the spinal cord of adult rats results in the extension of processes from intrinsic spinal cord neurons out into the root. After implantation of avulsed ventral roots into the ventro-lateral aspect of the cord, axonal regrowth and functional restitution of alpha-motoneurons could be demonstrated by intracellular recordings and injections with horseradish peroxidase. These results show that regeneration can occur across a PNS-CNS interface that has been established secondary to a trauma in the mature animal and in the immature animal before the astrocyte-rich CNS root segment has been developed.

Age Factors↗
PubMed2004

Sugar utilization and anoxia tolerance in rice roots acclimated by hypoxic pretreatment.

Although most cereal roots cannot elongate under anoxic conditions, primary roots of three-day-old rice (Oryza sativa L.) seedlings were able to elongate during a 24-h period of anoxia. Hypoxic pretreatment (H-PT) increased the elongation of their roots. Sucrose synthase (EC 2.4.1.13), glucokinase (EC 2.7.1.2), fructokinase (EC 2.7.1.4), pyruvate decarboxylase (EC 4.1.1.1) and alcohol dehydrogenase (EC 1.1.1.1) activities were increased by anoxia in both H-PT and non-pretreated (N-PT) roots. However, these activities were greater in the H-PT roots than in the N-PT roots. The average rate of production of ethanol for the initial 6h after the onset of anoxia was 3.7 and 1.4 micromolg(-1) fresh weight h(-1) for the H-PT and N-PT roots, respectively, suggesting that ethanolic fermentation may increase more quickly in the H-PT roots than in the N-PT roots. Roots of the seedlings lost ATP and total adenine nucleotides in anoxia, however, the H-PT roots maintained higher levels of ATP and total adenine nucleotides compared to the N-PT roots. These results show that rice roots are able to utilize the set of enzymes involved in the metabolism of soluble sugars under anoxia. The ability to maintain an active fermentative metabolism for production of ATP by fueling the glycolytic pathway with fermentable carbohydrate is probably greater in H-PT than in N-PT roots.

Acclimatization↗
PubMed1998

Microleakage along apical root fillings and cemented posts.

STATEMENT OF PROBLEM: Coronal leakage of endodontically treated teeth has been found to result in a high failure rate. PURPOSE: This study tested leakage along apical root fillings remaining after post space preparation and cemented posts in root canals. MATERIAL AND METHODS: A total of 120 human roots were used in the study and divided into six groups, 20 roots for each group. By using a modified fluid transport model, leakage (in microL/hr) along ParaPost dowels that were cemented in the coronal 7 mm of root canals with Fuji Duet, Ketac Cem, Panavia EX, or zinc phosphate cements was compared with that along the coronal 7 mm of conventional root canal fillings. Leakage along the apical 4 mm of root filling remaining after post space preparation was compared with that along the 11 mm root filling before post space preparation. RESULTS: More leakage was recorded along the apical 4 mm of root filling than along the 11 mm of original root filling (p = 0.0325). ParaPost dowels cemented with any test cement did not produce more leakage than the 7 mm coronal root filling (p = 0.2145). CONCLUSIONS: The apical 4 mm of root canal filling remaining after post space preparation leaks statistically significantly more than the original full-length root canal filling. The leakage created by removal of the coronal part of root canal filling during post space preparation may be compensated by the cemented posts.

Analysis of Variance↗
PubMed1995

Comparative investigation of marginal adaptation of mineral trioxide aggregate and other commonly used root-end filling materials.

This study investigated the marginal adaptation of mineral trioxide aggregate (MTA) as a root-end filling material, compared with commonly used root-end filling materials by scanning electron microscopy (SEM). Eighty-eight single-rooted freshly extracted human teeth were cleaned, shaped, and obturated with gutta-percha and root canal sealer. Following root-end resection and cavity preparation, the root-end cavities were filled with amalgam, Super-EBA, Intermediate Restorative Material (IRM), or MTA. Using a slow-speed diamond saw, 40 roots were longitudinally sectioned into two halves. Resin replicas of resected root ends of the remaining nonsectioned roots were also prepared. After mounting longitudinal sections of roots and resin replicas of resected roots on aluminum stubs, the distance between the test root-end filling materials and surrounding dentin was measured at four points under SEM. Examination of the original samples showed numerous artifacts in the longitudinal sections of the specimens. In contrast, the resin replicas of resected and filled root ends had no artifacts. Statistical analysis of data comparing gap sizes between the root-end filling materials and their surrounding dentin shows that MTA had better adaptation compared with amalgam, Super-EBA, and IRM.

Aluminum Compounds↗
PubMed1998

Bacterial leakage of mineral trioxide aggregate as compared with zinc-free amalgam, intermediate restorative material, and Super-EBA as a root-end filling material.

Several dye leakage studies have demonstrated the fact that mineral trioxide aggregate (MTA) leaks significantly less than other root-end filling materials. The purpose of this study was to determine the time needed for Serratia marcescens to penetrate a 3 mm thickness of zinc-free amalgam, Intermediate Restorative Material (IRM), Super-EBA, and MTA when these materials were used as root-end filling materials. Fifty-six, single-rooted extracted human teeth were cleaned and shaped with a series of .04 Taper rotary instruments (Pro-series 29 files). Once the canals were prepared in a crown down approach, the ends were resected and 48 root-end cavities were ultrasonically prepared to a 3 mm depth. The teeth were then steam sterilized. Using an aseptic technique, under a laminar air flow hood, the root-end cavities were filled with amalgam, IRM, Super-EBA, and MTA. Four root-end cavities were filled with thermoplasticized gutta-percha without a root canal sealer and served as positive controls. Another four root-end cavities were filled with sticky wax covered with two layers of nail polish and served as negative controls. The teeth were attached to presterilized (ethylene oxide gas) plastic caps, and the root ends were placed into 12-ml vials of phenol red broth. Using a micropipette, a tenth of a milliliter of S. marcescens was placed into the root canal of each tooth. To test the sterility of the apparatus set-up, the root canals of two teeth with test root-end filling materials and one tooth from the positive and negative control groups were filled with sterile saline. The number of days required for S. marcescens to penetrate the four root-end filling materials and grow in the phenol red broth was recorded and analyzed. Most of the samples filled with zinc-free amalgam leaked bacteria in 10 to 63 days. IRM began leaking 28 to 91 days. Super-EBA began leaking 42 to 101 days. MTA did not begin leaking until day 49. At the end of the study, four of the MTA samples had not exhibited any leakage. Statistical analysis of the data indicated Mineral Trioxide Aggregate to be a most effective root-end filling material against penetration of S. marcescens.

Aluminum Compounds↗
PubMed2004

Coumarin differentially affects the morphology of different root types of maize seedlings.

The effects of coumarin on the length, diameter, and branching density of different root types in maize seedlings (Zea mays L. cv. Cecilia) were investigated. The maize root system represents a useful model for morphological studies, as it consists of radicle, seminal, and nodal roots whose origin and development are quite different. Maize seedlings were grown in a hydroponic culture for 6 days, and then coumarin (at concentrations of 0, 25, 100, and 400 microM) was added to the nutrient solution. Coumarin inhibited root length, but effects differed depending on the root type. C 1/2 values, representing the coumarin concentration causing a 50% inhibition of the root length, were calculated by nonlinear regression. Six, 1, and 0.25 mM coumarin were sufficient to reduce the radicle, seminal, and nodal root lengths by 50%, respectively. At the highest coumarin concentration, the subapical root zone showed swelling. The degree recorded by average diameter was higher in nodal roots than in seminal and radicle roots. Furthermore, coumarin decreased the number of lateral roots and branching density more in the seminal than in the radicle roots. These results suggest the following order of sensitivity to coumarin: nodal > seminal > radicle roots. The observed spatial effects of coumarin could be ecologically significant, since taprooted species could benefit at the disadvantage of fibrous-rooted species and could modify community composition.

Coumarins↗
PubMed2002

A comparative study of root canal preparation using Profile .04 and Lightspeed rotary Ni-Ti instruments.

AIM: The purpose of this Study was to compare several parameters of root canal preparation using two different rotary nickel-titanium instruments: ProFile .04 (Dentsply/ Maillefer, Ballaigues, Switzerland) and Lightspeed (Lightspeed Technology Inc., San Antonio, TX, USA). METHODOLOGY: Fifty extracted mandibular molars with root canal curvatures between 20 degrees and 40 degrees were divided into two similar groups having equal mean curvatures. The teeth were then embedded into a muffle system as described by Bramante et al. (1987) and modified by Hülsmann et al. (1999b). All root canals were prepared using ProFile .04 or Lightspeed Ni-Ti instruments to size 45 following the manufacturers' instructions. The Lightspeed system was used in a step-back technique: ProFile .04 instruments were used in a crown-down technique. The following parameters were evaluated: straightening of curved root canals (superimposition of pre- and postoperative radiographs), postoperative root canal diameter (superimposition of pre- and postoperative photographs of root canal cross-sections), safety issues (file fractures. perforations, apical blockages, loss of working length) (protocol), cleaning ability (SEM-evaluation of root canal walls using a five-score system for debris and smear layer), and working time (protocol). Statistical analysis was performed using the Wilcoxon test (P < 0.05) for straightening, and Fisher's exact-test (P < 0.05) for comparison of cross-sections, for comparison of contact between pre- and postoperative diameter, root canal cleanliness and working time. RESULTS: Both Ni-Ti systems maintained curvature well; the mean degree of straightening was less than 1 degrees for both ProFile .04 and for Lightspeed with no statistical significance between the groups. Most procedural incidents occurred with Profile .04 instruments (three fractures), Lightspeed preparation was completed without instrument fractures. Loss of working length, perforations or apical blockage did not occur with either instrument. Following preparation with Profile.04. 64.0% of the root canals had a round, 30.7% an oval, and 5.3% an irregular cross-section, Lightspeed preparation resulted in a round cross-section in 41.3% of cases, an oval shape in 45.3% of cases: 13.3% of cases had an irregular cross-section. No significant differences were found between the two systems. Lightspeed instruments enlarged the root canal more uniformly with no specimen showing 50% or more contact between pre- and postoperative diameter. The difference was statistically significant only for the coronal third of the root canals (P = 0.032). Mean working time was significantly shorter for Profile .04 (105 s) than for Lightspeed (140 s) (P = 0.02). For debris removal Lightspeed achieved the best results (68% scores 1 and 2), followed by Profile .04 (48.4%) with no significant differences between the systems. The results for remaining smear layer were similar: the lowest amount of smear layer on the root canal walls was found after preparation with Lightspeed (30.7% scores 1 and 2). followed by Profile.04 (23.1%). In the coronal third of the root canals Lightspeed performed significantly better than Profile .04 (P = 0.029): in the middle and apical third the differences were not significant. CONCLUSIONS: Both systems under investigation respected original root canal curvature and were safe to use. Both systems can be recommended for clinical use.

Dental Alloys↗
PubMed2004

Root system architecture of Quercus pubescens trees growing on different sloping conditions.

BACKGROUND AND AIMS: Plant roots' growth direction has important implications for plant development and survival; moreover it plays an effective and vital role in stabilizing weathered soil on a steep slope. The aim of this work was to assess the influence of slope on the architecture of woody root systems. METHODS: Five mature, single-stemmed Quercus pubescens trees growing on a steep slope and five on a shallow slope were excavated to a root diameter of 1 cm. A very precise numeric representation of the geometry and topology of structural root architecture was gained using a low-magnetic-field digitizing device (Fastrak, Polhemus). Several characteristics of root architecture were extracted by macros, including root volume, diameter, length, number, spatial position and branching order. KEY RESULTS: The diameter at breast height (dbh) was the best predictor of the root volume but had no correlation with length and number of roots. The slope affected the root volume for each branching order, and the basal cross-sectional area (CSA), number and length of the first-order roots. Number and length of the second- and third-order laterals were closely related in both conditions, although this relationship was closer in the shallow trees, suggesting the influence of a genetic control. Sloping trees showed a clustering tendency of the first- and second-order lateral roots in the up-slope direction, suggesting that the laterals rather than the taproots provide much of the anchorage. In a steep-slope condition, the taproot tapering was positively correlated with the asymmetry magnitude of first-order roots, indicating compensation between taproot and main lateral roots' clustering tendency. CONCLUSIONS: These results suggest that on a slope, on clayey soils, root asymmetry appears to be a consequence of several environmental factors such as inclination, shallow-slides and soil compactness. In addition, this adaptive growth seems to counteract the turning moment induced by the self-loading forces acting in slope conditions, and as a consequence improves the tree stability.

Environment↗
PubMed2006

Heterogeneity in spatial P-distribution and foraging capability by Zea mays: effects of patch size and barriers to restrict root proliferation within a patch.

BACKGROUND AND AIMS: Localized proliferation of roots in nutrient-enriched patches seems to be an adaptive response in many plants, but its function is still debatable. To understand the efficiency and limitation of foraging behaviour, the impact of patch size and the presence or absence of a barrier to root proliferation within phosphorus (P)-enriched patches was examined. METHODS: In pots filled with P-poor soil, six treatments of heterogeneous P supply were prepared: three patch sizes with or without a root barrier between patches. In addition, a homogeneous P supply treatment was also prepared. Irrespective of these treatments, each pot received the same total amount of P. Maize (Zea mays) was grown in each pot for 45 d in a greenhouse. KEY RESULTS: P content and biomass were greatest in plants grown in the largest patch due to successful root proliferation, and were higher in the presence of a root barrier. Interestingly, plants preferentially developed adventitious nodal roots projecting from the stem into the P-enriched soil, particularly in the largest patch with a root barrier. Removal of the barrier reduced the P-uptake capacity per unit root surface area or volume in P-enriched patches, revealing that the P-uptake capacity per root can be suppressed even in P-rich soil if other portions on the root axis encounter P-poor conditions. CONCLUSIONS: The results suggest that the efficiency of root morphological plasticity is largely determined by the size of the P-enriched patch. Furthermore, the results imply a novel aspect of P-uptake physiology that roots in heterogeneous P cannot demonstrate their potential capacity, as would be observed in roots encountering P continuously; this effect is probably mediated by an internal root factor.

Nitrogen↗
PubMed1990

A long-term study of 370 autotransplanted premolars. Part IV. Root development subsequent to transplantation.

The purpose of the present study was to analyse the extent of root development subsequent to transplantation in a material of 370 transplanted premolars. Before transplantation, the grafts were classified according to stage of root development (i.e. quarters of root length and constriction of the apical foramen) and length of tooth development (measured in mm from the cusp tip to the apical foramen). At radiographic controls the extent of root formation was registered. These figures were compared to the final tooth length of 288 non-transplanted premolars from the present material as well as to tooth length determinations of 534 premolars extracted for orthodontic purposes. Furthermore, intra-individual and inter-individual differences in tooth length were examined in a skull material with 40 pairs of premolars. These method studies indicated that root growth was probably determined genetically with great right-left accuracy and variation related to location of premolar (maxilla or mandible) and sex. A statistical analysis of the transplant material revealed that stage as well as length of tooth development assessed prior to transplantation were significantly related to final tooth length after transplantation. In most cases of transplantation performed at early stages of root development, a reduction in the final root length was seen. When a qualitative analysis of root development was performed in teeth with incomplete root formation at the time of transplantation, and where a homologous non-transplanted premolar was present, it was found that 14 per cent showed total arrest of root formation, 65 per cent partial arrest whereas 21 per cent showed no arrest (i.e. normal root formation). Premolars in ectopic position in the mandible before transplantation showed a significantly reduced root growth compared to matched pairs with normal position of the tooth graft. The present study indicated that no, partial or total damage to the Hertwig's epithelial root sheath was probably the explanatory factor for variations in root growth.

Adolescent↗
PubMed2000

Agrobacterium rhizogenes-mediated transformation of opium poppy, Papaver somniferum l., and California poppy, Eschscholzia californica cham., root cultures.

An efficient protocol for the establishment of transgenic opium poppy (Papaver somniferum L.) and California poppy (Eschscholzia californica Cham.) root cultures using A. grobacterium rhizogenes is reported. Five strains of A. rhizogenes were tested for their ability to produce hairy roots on wounded opium poppy seedlings and California poppy embryogenic calli. Three of the strains induced hairy root formation on both species, whereas two others either caused the growth of tumorigenic calli or produced no response. To characterize the putative transgenic roots further, explant tissues were co-cultivated with the most effective A: rhizogenes strain (R1000) carrying the pBI121 binary vector. Except for the co-cultivation medium, all formulations included 50 mg l(-1) paromomycin to select for transformants and 200 mg l(-1) timentin to eliminate the Agrobacterium. Four weeks after infection, paromomycin-resistant roots appeared on 92-98% of explants maintained on hormone-free medium. Isolated hairy roots were propagated in liquid medium containing 1.0 mg l(-1) indole-3-acetic acid to promote rapid growth. Detection of the neomycin phosphotransferase gene, high levels of beta-glucuronidase (GUS) transcripts and enzyme activity, and GUS histochemical localization confirmed the integrative transformation of root cultures. Transgenic roots grew faster than wild-type roots, and California poppy roots grew more rapidly than those of opium poppy. With the exception of a less compact arrangement of epidermal cells and more root hairs, transformed roots of both species displayed anatomical features and benzylisoquinoline alkaloid profiles that were virtually identical to those of wild-type roots. Transgenic root cultures of opium poppy and California poppy are a simple, reliable and well-defined model system to investigate the molecular and metabolic regulation of benzylisoquinoline alkaloid biosynthesis, and to evaluate the genetic engineering potential of these important medicinal plants.

Alkaloids↗
PubMed2001

Hydraulic conductivity of rice roots.

A pressure chamber and a root pressure probe technique have been used to measure hydraulic conductivities of rice roots (root Lp(r) per m(2) of root surface area). Young plants of two rice (Oryza sativa L.) varieties (an upland variety, cv. Azucena and a lowland variety, cv. IR64) were grown for 31-40 d in 12 h days with 500 micromol m(-2) s(-1) PAR and day/night temperatures of 27 degrees C and 22 degrees C. Root Lp(r) was measured under conditions of steady-state and transient water flow. Different growth conditions (hydroponic and aeroponic culture) did not cause visible differences in root anatomy in either variety. Values of root Lp(r) obtained from hydraulic (hydrostatic) and osmotic water flow were of the order of 10(-8) m s(-1) MPa(-1) and were similar when using the different techniques. In comparison with other herbaceous species, rice roots tended to have a higher hydraulic resistance of the roots per unit root surface area. The data suggest that the low overall hydraulic conductivity of rice roots is caused by the existence of apoplastic barriers in the outer root parts (exodermis and sclerenchymatous (fibre) tissue) and by a strongly developed endodermis rather than by the existence of aerenchyma. According to the composite transport model of the root, the ability to adapt to higher transpirational demands from the shoot should be limited for rice because there were minimal changes in root Lp(r) depending on whether hydrostatic or osmotic forces were acting. It is concluded that this may be one of the reasons why rice suffers from water shortage in the shoot even in flooded fields.

Biological Transport↗