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PubMedDate not supplied

Isoflavonoid accumulation in soybean hairy roots upon treatment with Fusarium solani.

Hairy roots were initiated from two soybean [Glycine max (L.) Merr.] genotypes with different susceptibility (susceptible 'Spencer' and partially resistant 'PI567.374') to the disease sudden death syndrome (SDS) caused by the soil-borne fungal pathogen Fusarium solani f. sp. glycines (FSG) to study the role of isoflavonoids in the plant response to FSG infection. Hairy root cultures obtained by transformation with Agrobacterium rhizogenes allows normal root growth that can be visually monitored. The principal isoflavones (genistin, daidzin, glycitin and their malonyl conjugates and aglycones) and also isoflavonoid phytoalexins (coumestrol and glyceollin) were measured by HPLC in extracts of the FSG-inoculated and non-inoculated hairy roots. FSG mycelia grew more slowly on inoculated PI567.374 hairy roots than on Spencer hairy roots. The glyceollin content was higher in FSG-inoculated PI567.374 hairy roots than in Spencer hairy roots even though the glyceollin precursor, the isoflavone daidzein, was higher in Spencer. The de novo synthesis of isoflavones and glyceollin was confirmed by [(14)C]Phe incorporation into glyceollin, which was higher both in the FSG-inoculated roots and surrounding medium of the cv. PI567.374 than that of Spencer. Glyceollin was the most inhibitory to FSG growth among eight isoflavonoids tested. The levels of coumestrol, a putative phytoalexin, did not change upon FSG inoculation. The defense response was also elicited by FSG culture filtrates in hairy roots grown in liquid culture. The data obtained indicate that the ability of soybean roots to rapidly produce sufficient amounts of glyceollin in response to FSG infection might be important in providing partial resistance to this fungus.

Benzopyrans↗
PubMed1997

Toxin I, but not 4-aminopyridine, blocks the late inhibitory component of the dorsal root reflex in an isolated preparation of rat spinal cord.

Bursts of spontaneous antidromic dorsal root action potentials, and evoked dorsal root reflexes (DRR), have been recorded from lumbar roots of isolated spinal cord preparations of rats weighing 70-90 g. The pattern of dorsal root activity was similar to that reported for isolated cord preparations from hamsters, but the frequency of spontaneous dorsal root activity was approximately 10 times slower in the rat. Toxin I and 4-aminopyridine (4-AP) both increased the frequency of spontaneous dorsal root activity. The threshold concentration of 4-AP was 1 microM, with EC50 at 20 microM. Insufficient Toxin I was available to reach a maximal response, but the threshold concentration for producing an increase in spontaneous activity was 0.1 microM, and the curve appeared to be parallel to that of 4-AP. The patterns of spontaneous dorsal root activity in the presence of 4-AP and Toxin I differed. In 4-AP bursts of large amplitude action potentials were followed by periods of depressed activity lasting up to 500 ms, whereas in Toxin I bursts of large amplitude action potentials caused no change in the continuously firing small amplitude action potentials. DRR evoked by stimulation of adjacent dorsal roots also showed differences in the presence of 4-AP and Toxin I. In 4-AP the excitatory phase of the reflex was followed by a period of depressed activity lasting up to 500 ms. This was was reduced or absent in the presence of Toxin I. Paired pulse stimulation confirmed the presence of inhibition in 4-AP, and its reduction in Toxin I. Examination of the pattern of spontaneous dorsal root activity following dorsal root stimulation showed strong oscillatory activity in the presence of 4-AP, but little such activity in the presence of Toxin I. It was concluded that the actions of 4-AP and Toxin I on the isolated preparation of rat spinal cord are similar in that both cause an increase in the spontaneous dorsal root firing rate, but that Toxin I also blocks the period of inhibition which follows bursts of large amplitude action potentials.

4-Aminopyridine↗
PubMed1991

A comparison of anxiety levels associated with root canal therapy and oral surgery treatment.

Questionnaires regarding experience, hearsay, and perceptions of anxiety toward eight dental treatments were distributed to a general patient population. Data revealed that among 349 respondents 35% heard that root canal therapy was the most unpleasant dental treatment, whereas 29% listed oral surgery treatment as having the worst reputation. However, 53% of those experiencing oral surgery treatment stated that an oral surgery treatment was the most unpleasant treatment whereas only 17% experiencing root canal therapy stated the same for root canal therapy. On the basis of anxiety scores, root canal therapy and oral surgery treatment were categorized in the high-anxiety category, crowns, dentures, and fillings in the moderate-anxiety category, and cleaning, sick call, and examination in the low-anxiety category. The anxiety levels of root canal therapy and oral surgery treatment were then analyzed as they related to different experience groups (combinations of root canal therapy and oral surgery and experience), hearsay experience, and most unpleasant experience with root canal therapy and oral surgery. Patients having experience with root canal therapy or oral surgery treatment had lower anxiety levels toward these respective treatments than did those who had no such experience. Patients who have heard negative stories (hearsay) of root canal therapy and oral surgery showed higher levels of anxiety toward these respective treatments than did those who have not heard such stories. But former endodontic patients who had heard negative stories about root canal therapy actually recorded lower anxiety levels toward root canal therapy than those patients with no negative hearsay experience.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Anxiety↗
PubMed2004

Healing of periodontal defects treated with enamel matrix proteins and root surface conditioning--an experimental study in dogs.

Application of enamel matrix proteins has been introduced as an alternative method for periodontal regenerative therapy. It is claimed that this approach provides periodontal regeneration by a biological approach, i.e. creating a matrix on the root surfaces that promotes cementum, periodontal ligament (PDL) and alveolar bone regeneration, thus mimicking the events occurring during tooth development. Although there have been numerous in vitro and in vivo studies demonstrating periodontal regeneration, acellular cementum formation and clinical outcomes via enamel matrix proteins usage, their effects on the healing pattern of soft and hard periodontal tissues are not well-established and compared with root conditioning alone. In the present study, the effects of Emdogain (Biora, Malmö, Sweden), an enamel matrix derivative mainly composed of enamel matrix proteins (test), on periodontal wound healing were evaluated and compared with root surface conditioning (performed with 36% orthophosphoric acid) alone (control) histopathologically and histomorphometrically by means of the soft and hard tissue profile of periodontium. An experimental periodontitis model performed at premolar teeth of four dogs were used in the study and the healing pattern of periodontal tissues was evaluated at days 7, 14, 21, 28 (one dog at each day), respectively. At day 7, soft tissue attachment evaluated by means of connective tissue and/or epithelial attachment to the root surfaces revealed higher connective tissue attachment rate in the test group and the amount of new connective tissue proliferation in the test group was significantly greater than the control group (p<0.01). New bone formation by osteoconduction initiated at day 14 in the test and control group. At day 21, the orientation of supra-alveolar and PDL fibers established, and new cementum formation observed in both groups. At day 28, although regenerated cementum was cellular in all of the roots in the control samples, an acellular type of cementum (1.32+/-0.83 mm in length and 3.16+/-0.23 microm in width) was also noted in six roots of test samples with an inconsistent distribution on the root surfaces. The amount of new cementum was significantly higher in the test group than the control group samples (p<0.01). The width of the cellular cementum in the control group was more than the cellular cementum in the test group, but the difference was not statistically significant (p>0.05). A firm attachment of acellular cementum to the root dentin with functional organization of its collagen fibers was noted, and, the accumulation and organization of cellular cementum in the control group was more irregular than the cellular cementum formed in the test group. The amount of new bone was 2.41+/-0.75 mm in the test and 1.09+/-0.46 mm in the control group at day 28. The rate of bone maturation (the number of osteons) was found higher in the test group (10.75+/-0.85) than the control group (5.50+/-0.86). Under the limitations of the study, our results reveal that when compared with root surface conditioning, enamel matrix proteins have more capacity for stimulating periodontal regeneration via their positive effects on root surfaces, i.e. inhibition of gingival epithelium down growth and stimulation of connective tissue proliferation and attachment to the root surfaces during wound healing. An acellular type of cementum regeneration and new alveolar bone formation by an accelerated osteoconductive mechanism are also achieved with application of enamel matrix proteins.

Animals↗
PubMed2003

Genetic analysis of the gravitropic set-point angle in lateral roots of Arabidopsis.

Research on gravity responses in plants has mostly focused on primary roots and shoots, which typically orient to a vertical orientation. However, the distribution of lateral organs and their characteristically non-vertical growth orientation are critical for the determination of plant form. For example, in Arabidopsis, when lateral roots emerge from the primary root, they grow at a nearly horizontal orientation. As they elongate, the roots slowly curve until they eventually reach a vertical orientation. The regulation of this lateral root orientation is an important component affecting overall root system architecture. We found that this change in orientation is not simply due to the onset of gravitropic competence, as non-vertical lateral roots are capable of both positive and negative gravitropism. Thus, the horizontal growth of new lateral roots appears to be determined by what is called the gravitropic set-point angle (GSA). This developmental control of the GSA of lateral roots in Arabidopsis provides a useful system for investigating the components involved in regulating gravitropic responses. Using this system, we have identified several Arabidopsis mutants that have altered lateral root orientations but maintain normal primary root orientation.

Arabidopsis↗
PubMed2001

Evaluation of extracts of the root of Landolphia owerrience for antibacterial activity.

Ethanolic and aqueous (cold and hot) extracts of Landolphia owerrience root parts (whole-root, root-bark and root-wood) were tested for activity against ten bacterial strains using agar-well diffusion and macro-broth dilution methods, respectively. The ethanolic extracts of the whole-root and root-wood were active against 100 and 80% of the test organisms, respectively. Ethanolic and aqueous extracts of the root-bark were moderately active while the aqueous (cold and hot) extracts of the root-wood exhibited little or no activity. Out of the nine extracts prepared, 66.7% were active against Staphylococcus aureus ATCC 12600, 55.6% variously against each of Pseudomonas aeruginosa ATCC 10145 and local clinical isolates of P. aeruginosa, S. aureus, Escherichia coli and Salmonella typhi, 44.4% against Proteus sp., 33.3% against Bacillus subtilis ATCC 6051 and 22.2% against E. coli ATCC 11775. The agar-well-determined MIC values for the ethanolic whole-root extract (0.78-50 mg/ml) were higher (indicating lower activity) than the corresponding macro-broth-determined values (0.39-50 mg/ml) probably because of slow diffusion rates of the active constituents of the extract in agar. On the other hand, the differences could be due to the effects of DMSO used to dissolve the ethanolic extracts in the agar-well diffusion tests. Similar discrepancies in the MIC values detectable with the two test methods were apparent in the root-wood extract and the control drug, Gentamycin, except that in the latter the agar-well-determined MIC values (0.125-8.0 microg/ml) were lower than the macro-broth-determined values (0.125-64 microg/ml). The strong activity of the ethanolic extracts against known etiologic agents of diseases traditionally treated with L. owerrience root of similar preparations provides scientific justification for the use of the herb in ethnomedical practice in Nigeria.

Anti-Infective Agents↗
PubMed1993

Root resorption after orthodontic treatment: Part 2. Literature review.

All permanent teeth may show microscopic amounts of root resorption that are clinically insignificant and radiographically undetected. Root resorption of permanent teeth is a probable consequence of orthodontic treatment and active tooth movement. The incidence of reported root resorption during orthodontic treatment varies widely among investigators. Usually, extensive resorption does not affect the functional capacity or the effective life of the tooth. Most studies agree that the root resorption process ceases once the active treatment is terminated. Root resorption of the deciduous dentition is a normal, essential, and physiologic process. Permanent teeth have the potential to clinically undergo significant external root resorption when affected by several stimuli. This resorptive potential varies in persons and between different teeth in the same person. This throws doubt on the role of systemic factors as a primary cause of root resorption during orthodontic treatment. Tooth structure, alveolar bone structure at various locations, and types of movement may explain these variations. The extent of treatment duration and mechanical factors definitely influence root resorption. In most root resorption studies, it is not possible to compare the results and conclusions because of their different methods. Further research in this field is necessary to advance the service of the specialty. The question of whether there is an optimal force to move teeth without resorption or whether root resorption may be predictable remain unanswered. This review indicates the unpredictability and widespread incidence of the root resorption phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1999

External apical root resorption of posterior teeth in asthmatics after orthodontic treatment.

External apical root resorption is an undesirable sequela of orthodontic treatment, resulting in loss of tooth structure from the root apex. It has been proposed that systemic factors, such as the inflammatory mediators produced in asthma, may enter the periodontal ligament and act synergistically to enhance root resorption. The aim of this study was to determine if asthmatic patients exhibited a higher incidence or severity of external apical root resorption compared with healthy (no medical conditions) patients after fixed orthodontic treatment. Records were obtained from patients treated with fixed appliances; 99 were healthy and 44 had asthma. Using OPGs (panoral films), posterior external apical root resorption was measured on all first and second premolars, mesiobuccal and distobuccal roots of the upper first molars, and mesial and distal roots of the lower first molars, giving 4 measurements per quadrant. A 4-grade ordinal scale was used to determine the degree of external apical root resorption. Combined tooth analysis (adjusted for treatment time, appliance, and extractions) showed that asthmatics had significantly more external apical root resorption of posterior teeth after treatment compared with the healthy group (P =.0194). Tooth-by-tooth analysis (adjusted for treatment time, appliance, extractions, headgear, overbite, overjet, sex, and age at start of treatment) found the upper first molars were most susceptible to external apical root resorption. Although the incidence of external apical root resorption was elevated in the asthma group, both asthmatics and healthy patients exhibited similar amounts of grade 2 (moderate) and grade 3 (severe) resorption.

Adult↗
PubMedDate not supplied

Hairy root culture in a liquid-dispersed bioreactor: characterization of spatial heterogeneity.

A liquid-dispersed reactor equipped with a vertical mesh cylinder for inoculum support was developed for culture of Atropa belladonna hairy roots. The working volume of the culture vessel was 4.4 L with an aspect ratio of 1.7. Medium was dispersed as a spray onto the top of the root bed, and the roots grew radially outward from the central mesh cylinder to the vessel wall. Significant benefits in terms of liquid drainage and reduced interstitial liquid holdup were obtained using a vertical rather than horizontal support structure for the biomass and by operating the reactor with cocurrent air and liquid flow. With root growth, a pattern of spatial heterogeneity developed in the vessel. Higher local biomass densities, lower volumes of interstitial liquid, lower sugar concentrations, and higher root atropine contents were found in the upper sections of the root bed compared with the lower sections, suggesting a greater level of metabolic activity toward the top of the reactor. Although gas-liquid oxygen transfer to the spray droplets was very rapid, there was evidence of significant oxygen limitations in the reactor. Substantial volumes of non-free-draining interstitial liquid accumulated in the root bed. Roots near the bottom of the vessel trapped up to 3-4 times their own weight in liquid, thus eliminating the advantages of improved contact with the gas phase offered by liquid-dispersed culture systems. Local nutrient and product concentrations in the non-free-draining liquid were significantly different from those in the bulk medium, indicating poor liquid mixing within the root bed. Oxygen enrichment of the gas phase improved neither growth nor atropine production, highlighting the greater importance of liquid-solid compared with gas-liquid oxygen transfer resistance. The absence of mechanical or pneumatic agitation and the tendency of the root bed to accumulate liquid and impede drainage were identified as the major limitations to reactor performance. Improved reactor operating strategies and selection or development of root lines offering minimal resistance to liquid flow and low liquid retention characteristics are possible solutions to these problems.

Atropa belladonna↗
PubMed1997

Expression of glyoxylate cycle genes in cucumber roots responds to sugar supply and can be activated by shading or defoliation of the shoot.

When cucumber roots are excised and incubated without a carbon source, isocitrate lyase (ICL) and malate synthase (MS) mRNAs increase significantly in amount. However, if sucrose is added to the excised roots, the mRNAs do not accumulate. Hairy roots obtained by transformation with Agrobacterium rhizogenes show the same response. Transgenic hairy roots containing the Icl and Ms gene promoters fused to the GUS reporter gene, have very low GUS activity which increases dramatically when roots are incubated in the absence of sugar, indicating regulation at the transcriptional level. Staining of sugar-deprived roots shows that GUS activity is concentrated mainly in root tips and lateral root primordia, where demand for carbohydrate is greatest. In order to determine if Icl and Ms genes are expressed in roots of whole plants under conditions which may occur in nature, cucumber plants were subjected to reduced light intensity or defoliation. In both cases increases were observed in ICL and MS mRNAs. These treatments also reduced root sugar content, consistent with the hypothesis that sugar supply could control expression of Icl and Ms genes in roots of whole plants.

Cucumis sativus↗
PubMed2003

Modulation of berberine bridge enzyme levels in transgenic root cultures of California poppy alters the accumulation of benzophenanthridine alkaloids.

California poppy (Eschscholzia californica Cham.) root cultures produce a variety of benzophenanthridine alkaloids, such as sanguinarine, chelirubine and macarpine, with potent biological activity. Sense and antisense constructs of genes encoding the berberine bridge enzyme (BBE) were introduced into California poppy root cultures. Transgenic roots expressing BBE from opium poppy (Papaver somniferum L.) displayed higher levels of BBE mRNA, protein and enzyme activity, and increased accumulation of benzophenanthridine alkaloids compared to control roots transformed with a beta-glucuronidase gene. In contrast, roots transformed with an antisense-BBE construct from California poppy had lower levels of BBE mRNA and enzyme activity, and reduced benzophenanthridine alkaloid accumulation, relative to controls. Pathway intermediates were not detected in any transgenic root lines. Suppression of benzophenanthridine alkaloid biosynthesis using antisense-BBE also reduced the growth rate of the root cultures. Two-dimensional 1H-NMR spectroscopy showed no difference in the abundance of carbohydrate metabolites in the various transgenic roots lines. However, transformed roots with low levels of benzophenanthridine alkaloids contained larger cellular pools of certain amino acids compared to controls. In contrast, cellular pools of several amino acids were reduced in transgenic roots with elevated benzophenanthridine alkaloid levels relative to controls. The relative abundance of tyrosine, from which benzophenanthridine alkaloids are derived, was only marginally altered in all transgenic root lines; thus, altering metabolic flux through benzophenanthridine alkaloid pathways can affect cellular pools of specific amino acids. Consideration of such interactions is important for the design of metabolic engineering strategies that target benzophenanthridine alkaloid biosynthesis.

Alkaloids↗
PubMed2004

Manipulation of root hair development and sorgoleone production in sorghum seedlings.

Sorghum (Sorghum bicolor) roots exude a potent bioherbicide sorgoleone. Previous work indicates that sorgoleone is produced in living root hairs. We have developed a mist system that resulted in abundant production of root hairs exuding sorgoleone and a mat system that significantly inhibited root hair development and consequently sorgoleone production. Applying Ag+ (an ethylene action inhibitor) at 1.2 mM to the seedlings grown in the mist system also inhibited root hair formation and elongation. Hypoxic conditions in the mist system did not result in the inhibition of root hair growth as compared to the standard air atmosphere (20.8% O2). Applying ethephon (an ethylene-releasing agent) at 0.031 mM to the roots of seedlings grown in the mat system with water running at 1 ml/min reversed the inhibition of root hair development by water movement. These results indicate that either water movement or ethylene can be utilized to manipulate root hair development and sorgoleone production in sorghum seedlings. It is hypothesized that water movement reduced the local ethylene concentration on the root surface and consequently inhibited root hair development of sorghum seedlings grown in the mat system.

Benzoquinones↗
PubMed2004

Growth inhibition and root ultrastructure of cucumber seedlings exposed to allelochemicals from rye (Secale cereale).

Inhibition of "Calypso" cucumber seedling growth by rye allelochemicals, 2(3H)-benzoxazolinone BOA and 2,4-dihydroxy-1,4(2H)-benzoxazin-3-one DIBOA, was studied by analyzing the growth of seedling tissues and organs. Light and electron microscopy of seedling root cells were also carried out to investigate the mechanism(s) of root growth inhibition and mode of action of these compounds. BOA inhibited root elongation and reduced the number of cucumber lateral roots by 77 and 100% at 0.1 and 0.43 mg BOA/ml deionized (DI) water, respectively. DIBOA also inhibited root growth, but did not affect the number of lateral roots. BOA increased size of cucumber cortical root cells fivefold, but DIBOA had no effect. Both compounds reduced the regeneration of root cap cells and increased the width of cortical cells resulting in increased root diameter. BOA and DIBOA caused increased cytoplasmic vacuolation, reduced ribosome density and dictyosomes, reduced number of mitochondria, and reduced lipid catabolism. Starch granules in amyloplasts of seedling roots treated with BOA and DIBOA were also greatly reduced compared to the control. Changes in cellular ultrastructure indicated that BOA and DIBOA reduced root growth by disrupting lipid metabolism, reducing protein synthesis, and reducing transport or secretory capabilities.

Benzoxazines↗
PubMed2003

A preliminary in vitro study of the incidence and position of the root canal isthmus in maxillary and mandibular first molars.

AIM: To investigate in vitro the incidence and position of the root canal isthmus in extracted mesiobuccal roots of maxillary and mesial roots of mandibular first molars. METHODOLOGY: Fifty maxillary and 50 mandibular molars were included in the study. The mesiobuccal roots of maxillary molars and the mesial roots of mandibular molars were sectioned from their crowns in the furcation region and embedded in clear resin. Transverse serial 1-mm-thick sections from the apical 6 mm were prepared. The apical side of each section was stained with India ink and observed through a light microscope. The sample images were saved to disk using a digital camera and the root canals in terms of the number present and the incidence and classification of isthmuses. RESULTS: In the mesiobuccal root of the maxillary first molars, 70% had one canal, whereas 29.5% had two canals. In the mesial root of mandibular molars, 41% had one canal, whereas 59% had two canals. In some sections, more than two canals were found close to the apical foramen. The isthmus incidence was greatest 3-5 mm from the apex. In teeth having two canals, a complete or partial isthmus was frequently observed in the sections between 3 and 4 mm from the apex. Of the isthmuses present, 22% were complete and 37% partial in mandibular molars and 17.3% were complete and 11.7% partial in maxillary molars. CONCLUSIONS: The incidence of isthmus in the mesiobuccal root of the maxillary first molars and in the mesial root of the mandibular first molars was high, particularly in sections 3-5 mm from the apex. Cleaning the isthmus is a major challenge during root canal treatment.

Dental Pulp Cavity↗
PubMed1997

Mannitol inhibits growth of intact cucumber but not pea seedlings by mechanically collapsing the root pressure.

The positive xylem pressure (Px) in cucumber hypocotyls is a direct extension of root pressure and therefore depends on the root environment. Solutions of the electrolyte KCl (0-10 osm) reduced the hypocotyl Px transiently (biphasic response), while the Px reduction by mannitol solutions was sustained. The amplitudes of the induced Px reduction depended directly, and the degree of Px restoration after stress release depended indirectly, on the size of the initial positive Px indicating that mannitol released the root pressure by a mechanical rather than osmotic mechanism. Mannitol treatment and other means of root pressure reduction revealed two separate growth responses in the affected cucumber hypocotyls. Only steep Px drops (following root excision or root pressure release in mannitol) directly cause a rapid, transient drop in growth rate (GR). Both rapid and slow (after root incubation in KCN or NEM) decreases in root pressure, however, led to a sustained growth inhibition of cucumber hypocotyls after about 30 min. This delay characterizes the growth response as an indirect consequence of the Px change. Pea seedlings, which lacked root pressure and had a negative Px throughout, showed extremely small changes in epicotyl Px and GR after root incubation in mannitol. It is apparent that the higher sensitivity of cucumber growth to mannitol depended on the presence and release of root pressure.

Biological Transport, Active↗
PubMed2002

Dental CT evaluation of mandibular first premolar root configurations and canal variations.

OBJECTIVES: Routine dental CT scans were used to describe mandibular first premolar root configurations and canal variations. STUDY DESIGN: One hundred twenty dental CT examinations were evaluated for mandibular first premolar root configurations and canal variations regarding shape of root and root canal, incidence of multiple canals, and level of bifurcation. RESULTS: A total of 17 teeth in 12 patients showed mesial invagination of the root of the mandibular first premolar. One root displayed 3 canals with 3 apical foramina. In 2 teeth, a single canal divided into 2 canals, but merged into 1 apical foramen. One root showing 2 root canals finally divided into 2 roots near the apex. Thirteen roots had 2 canals and 2 apical foramina. The distance from the cementoenamel junction to the level of bifurcation was between 4 and 13 mm (mean, 7.4 mm). CONCLUSION: The occurrence of incidentally found mandibular first premolar root variations should be an important component of dental CT reports.

Bicuspid↗
PubMed2002

Structure and development of stomata on the primary root of Ceratonia siliqua L.

Stomata of various sizes are produced on the primary root of Ceratonia siliqua L. Most are generated during embryogenesis, prior to seed desiccation. They can be detected on the dry embryo in a wide zone just above the root tip. Initially, large stomata are formed. These have the ability to induce divisions of their neighbouring cells, creating particular cell patterns around them. Later, small perigenous stomata are generated. As the root grows following seed germination, the stomatal zone overlaps with that of the root hairs. Although root stomata of C. siliqua undergo a structural differentiation that seems almost identical to that of the elliptical stomata formed on leaves, they are unable to move and remain permanently open. Polarizing microscopy of fully differentiated stomata and young stomata at the stage of stomatal pore formation revealed deposition of radial cellulose microfibril systems on their periclinal walls. However, these systems were less developed than those on leaf stomata, a feature that might be responsible for their inactivity. Besides, plastids of the root guard cells (GCs) do not differentiate into chloroplasts but function solely as amyloplasts. Root stomata have a short life span. During rapid and intense root growth, GCs cannot keep pace with the elongation of their neighbouring rhizodermal cells. They therefore split in their mid-region, transversely to the stoma axis. The two parts of the transversely torn stoma are dragged apart and a large opening is formed on the root surface, just above the substomatal cavity. The root stomata, together with these openings, may facilitate increased gaseous exchange during respiration and/or an increased transfer of some nutrients and water in the rapidly growing primary root.

Cell Wall↗
PubMed2005

Selective transport of zinc, manganese, nickel, cobalt and cadmium in the root system and transfer to the leaves in young wheat plants.

BACKGROUND AND AIMS: The uptake, translocation and redistribution of the heavy metals zinc, manganese, nickel, cobalt and cadmium are relevant for plant nutrition as well as for the quality of harvested plant products. The long-distance transport of these heavy metals within the root system and the release to the shoot in young wheat (Triticum aestivum 'Arina') plants were investigated. METHODS: After the application of 65Zn, 54Mn, 63Ni, 57Co and 109Cd for 24 h to one seminal root (the other seminal roots being excised) of 54-h-old wheat seedlings, the labelled plants were incubated for several days in hydroponic culture on a medium without radionuclides. KEY RESULTS: The content of 65Zn decreased quickly in the labelled part of the root. After the transfer of 65Zn from the roots to the shoot, a further redistribution in the phloem from older to younger leaves was observed. In contrast to 65Zn, 109Cd was released more slowly from the roots to the leaves and was subsequently redistributed in the phloem to the youngest leaves only at trace levels. The content of 63Ni decreased quickly in the labelled part of the root, moving to the newly formed parts of the root system and also accumulating transiently in the expanding leaves. The 54Mn content decreased quickly in the labelled part of the root and increased simultaneously in leaf 1. A strong retention in the labelled part of the root was observed after supplying 57Co. CONCLUSIONS: The dynamics of redistribution of 65Zn, 54Mn, 63Ni, 57Co and 109Cd differed considerably. The rapid redistribution of 63Ni from older to younger leaves throughout the experiment indicated a high mobility in the phloem, while 54Mn was mobile only in the xylem and 57Co was retained in the labelled root without being loaded into the xylem.

Biological Transport, Active↗