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At least 1,621 records · Page 90Linked to original sources
PubMed1984

Interactions between ketamine and phencyclidine and dorsal root potentials (DRPs), evoked from the raphe nuclei.

Dorsal root potentials (DRPs) are thought to reflect presynaptic inhibition of primary afferent activity. Electrical stimulation of sites near the nucleus raphe magnus evokes two such potentials (DRP-1 and DRP-2) along dorsal roots of the lumbar and sacral spinal cord in the anaemically decerebrated cat. Dorsal root potential-2 is thought to be serotonergically mediated, while the neurochemical mediator of dorsal root potential-1 is not known. Serotonin antagonists selectively inhibit dorsal root potential-2 while the shorter latency dorsal root potential-1, which can be elicited anywhere in the brain stem, is potentiated by these drugs. The present study showed that most general anesthetics, such as ether or barbiturates, uniformly depressed both dorsal root potentials 1 and 2. The present studies indicate that two dissociative anesthetics, ketamine and phencyclidine, selectively inhibited dorsal root potential-2. This inhibitory effect of ketamine was dose-related, such that a dose of 11 mg/kg completely blocked dorsal root potential-2, but had no effect on dorsal root potential-1. Time-course studies indicated that the effect of phencyclidine on dorsal root potential-2 lasted much longer than that of ketamine. These results suggest that the effect of dissociative anesthetics on the descending pathways is unique compared to that of other anesthetic agents and that their effect correlates well in time-course and dose-range to their sedative/anesthetic effects.

Animals↗
PubMed2004

St. Jude Medical Toronto biologic aortic root prosthesis: early FDA phase II IDE study results.

BACKGROUND: Several biological aortic root replacement techniques have distinct advantages over mechanical composite root replacement including better valvular hemodynamic characteristics and the lack of need for anticoagulation. Current biological root replacement options lack proven long-term durability or are limited by technical or practical concerns. We report the early results from a phase II multicenter clinical trial of the porcine St. Jude Toronto Bioprosthesis with BiLinx (Toronto root). METHODS: 176 Toronto roots were implanted as total aortic root replacement from August 2001 through August 2003. Concomitant cardiac procedures including coronary artery bypass grafting (31%) and ascending aortic replacement (55%) were performed in 74%. Patients were followed clinically and were examined with an echocardiogram at discharge, 6 months, 12 months, and yearly thereafter. Root sizes implanted included 29 mm in 38%, 27 mm in 30%, 25 mm in 20%, 23 mm in 10%, and 21 mm in 2.2%. RESULTS: There are 205 patient years of follow-up through October 2003. Operative mortality was 3.9% (none were valve related) and late mortality was 4%. Operative stroke rate was 1.1% and late stroke rate was 0.6%. Endocarditis developed in 1 patient. Freedom from aortic regurgitation is to date 100% at discharge, 6 months, and 1 year postimplant. Reoperation of the aortic valve/root was not required in any patient. Six-month mean transvalvular gradients for 21-29 mm valves were 12.8, 8.8, 5.3, 4.9, and 4.7 mm Hg, respectively. CONCLUSIONS: Aortic root replacement with the Toronto root is safe and provides superb transvalvular hemodynamics with freedom from anticoagulation. The Toronto root seems widely applicable for all types of aortic root pathology and these early data offer very encouraging results. Long-term follow-up is required.

Adult↗
PubMed2006

Geometric models of the aortic and pulmonary roots: suggestions for the Ross procedure.

OBJECTIVE: To discuss geometric factors, which may influence long-term results relating to homograft competence following the Ross procedure, we describe the 3D morphology of the pulmonary and aortic roots. MATERIALS: Measurements were made on 25 human aortic and pulmonary roots. Inter-commissural distances and the heights of the sinuses were measured. For geometrical reconstruction the three commissures and their vertical projections at the root base were used as reference points. RESULTS: In the pulmonary root, the three inter-commissural distances were of similar dimensions (17.9+/-1.6mm, 17.5+/-1.4mm and 18.6+/-1.5mm). In the aortic root, the right inter-commissural distance was greatest (18.8+/-1.9mm), followed by the non-coronary (17.4+/-2.0mm) and left coronary sinus commissures (15.2+/-1.9mm). The mean height of the left pulmonary sinus was greatest (20+/-1.7mm) followed by the anterior (17.5+/-1.4mm) and right pulmonary sinus (18+/-1.66mm). In the aortic root, the height of the right coronary sinus was the greatest (19.4+/-1.9mm) followed by the heights of the non-coronary (17.7+/-1.8mm) and left coronary sinus (17.4+/-1.4mm). Measured differences between parameters determine the tilt angle and direction of the root vector. The tilt angle in the pulmonary root averaged 16.26 degrees , respectively; for the aortic roots, it was 5.47 degrees . CONCLUSIONS: Herein we suggest that the left pulmonary sinus is best implanted in the position of the right coronary sinus, the anterior pulmonary in the position of the non-coronary sinus and the right pulmonary sinus in the position of the left coronary sinus. In this way, the direction of the pulmonary root vector will be parallel to that of the aortic root vector.

Adult↗
PubMed2004

Further insights into normal aortic valve function: role of a compliant aortic root on leaflet opening and valve orifice area.

BACKGROUND: This study aims to find the fundamental differences in the mechanism of opening and closing of a normal aortic valve and a valve with a stiff root, using a dynamic finite element model. METHODS: A dynamic, finite element model with time varying pressure was used in this study. Shell elements with linear elastic properties for the leaflet and root were used. Two different cases were analyzed: (1) normal leaflets inside a compliant root, and (2) normal leaflets inside a stiff root. RESULTS: A compliant aortic root contributes substantially to the smooth and symmetrical leaflet opening with minimal gradients. In contrast, the leaflet opening inside a stiff root is delayed, asymmetric, and wrinkled. However, this wrinkling is not associated with increased leaflet stresses. In compliant roots, the effective valve orifice area can substantially increase because of increased root pressure and transvalvular gradients. In stiff roots this effect is strikingly absent. CONCLUSIONS: A compliant aortic root contributes substantially to smooth and symmetrical leaflet opening with minimal gradients. The compliance also contributes much to the ability of the normal aortic valve to increase its effective valve orifice in response to physiologic demands of exercise. This effect is strikingly absent in stiff roots.

Aortic Valve↗
PubMed2002

Dorsal root rupture injury induces extension of astrocytic processes into the peripheral nervous system and expression of GDNF in astrocytes.

Preganglionic brachial plexus injuries fall into two categories according to the lesion site, root avulsion injury and root rupture injury. The latter type of injury involves part of the peripheral nervous system (PNS) component at the injured spinal cord surface. Previous investigators have used rhizotomy of experimental animals as a model for dorsal root rupture injury. However, the effect on the central nervous system (CNS)-PNS junction accompanied by the mechanical stress from traction force is hard to estimate in this model. The current study aimed to demonstrate temporal molecular alterations from the CNS-PNS junction to the ruptured dorsal root after traction injury by immunohistochemical procedures. At 28 days after dorsal rupture injury, GFAP-positive structures could be clearly identified showing rather straight lines from the centro-peripheral junction toward the peripheral stump in the ruptured dorsal root. Immunoelectron microscopy for GFAP verified GFAP IR within the astrocytic processes at the injured dorsal root at 28 days after dorsal rupture injury. Glial cell line-derived neurotrophic factor immunoreactivity (GDNF IR) was slightly upregulated within the Schwann cell bodies on the injured dorsal root at 24-48 h after rupture injury. However, GDNF IR had appeared showing a process-like profile on the ruptured dorsal root by 28 days, and it was closely related with GFAP-positive structures. In contrast, a small increase in GFAP IR was only detected on the proximal side on the rhizotomized dorsal root at 28 days after rhizotomy. A marked decrease in NF IR and S-100 IR was observed at the ruptured dorsal root from 7 days. On the other hand, laminin IR was strongly upregulated on the ruptured dorsal root from 48 h to 7 days, and was still evident at 28 days. We therefore conclude that the astrocytes show a unique ability to extend their processes toward the stump. This ability may provide a new medium for the study of axonal regeneration in future clinical experiments.

Animals↗
PubMed2000

Genetic variability and molecular responses of root penetration in cotton.

Compacted soils restrict root penetration hindering productivity. In this paper, genetic variability of cotton (Gossipium spp.) root capacity to penetrate hard soil layers and the patterns of gene expression during penetration event were investigated. To mimic hard soil layers, wax-petrolatum mixtures were used. Genetic variability among 27 cotton genotypes for the root capacity to penetrate wax-petrolatum disks of 500-700 g wax/kg of mixture was high indicating that breeding efforts targeted to improve this trait can be successful. In the root tips of a cotton strain with high root penetrating ability (G. hirsutum HS 200) which penetrated through wax-petrolatum disks (P), quantity of four polypeptides with molecular weights 35-66 kDa increased compared to those root tips which grew in the absence of mechanical impedance (NP). Differential display showed significant differences in the sets of mRNA expressed in P and NP roots. Out of a total of 917 cDNAs scored in the differential display experiment, 118 cDNAs, or 13%, were specific to P roots and hence could be associated with the root penetration event. Further detailed study of gene expression in penetrated roots will pinpoint molecular factors involved in root penetration ability in cotton.

Journal Article↗
PubMed2000

Results of surgery for aortic root aneurysm in patients with the Marfan syndrome.

OBJECTIVE: To evaluate the results of two operations, aortic valve-sparing and aortic root replacement, in patients with aortic root aneurysm and the Marfan syndrome. METHODS: A retrospective review of 78 consecutive patients with aortic root aneurysm and the Marfan syndrome according to the Gent criteria indicated that 42 patients with normal aortic cusps had an aortic valve-sparing operation, and 36 patients had aortic root replacement (mechanical valve in 25 patients and biological valve in 11). The mean age was similar in both groups, but patients who had aortic root replacement had larger aneurysms, higher grade aortic insufficiency, worse left ventricular function and more cardiac co-morbidity than patients who had aortic valve-sparing operations. The mean follow-up was 41+/-35 months for patients who had aortic valve-sparing, and 65+/-50 months for those who had aortic root replacement. RESULTS: Kaplan-Meyer estimates of survival at 5 years was 100% for patients who had aortic valve-sparing, and 88+/-6% for those who had aortic root replacement (P=0.04). Five patients who had aortic root replacement required seven aortic root re-replacements: three for endocarditis and four for valve failure (biological valves). There have been no reoperations in patients who had aortic valve-sparing operations and annual Doppler echocardiography revealed mild or no aortic insufficiency in 39 patients and moderate aortic insufficiency in three. CONCLUSIONS: These data suggest that aortic valve-sparing operations are safe in patients with the Marfan syndrome and may provide better clinical outcomes than aortic root replacement. Since the size of the aneurysm often determines the feasibility of a valve-sparing procedure, we now recommend surgery when the diameter of the aortic root reaches 50 mm in patients with the Marfan syndrome who have echocardiographically normal aortic valve cusps.

Adolescent↗
PubMed2001

Response to auxin changes during maturation-related loss of adventitious rooting competence in loblolly pine (Pinus taeda) stem cuttings.

Hypocotyl cuttings (from 20- and 50-day-old Pinus taeda L. seedlings) rooted readily within 30 days in response to exogenous auxin, while epicotyl cuttings (from 50-day-old seedlings) rarely formed roots within 60 days. Responses to auxin during adventitious rooting included the induction of cell reorganization and cell division, followed by the organization of the root meristem. Explants from the bases of both epicotyl and hypocotyl cuttings readily formed callus tissue in response to a variety of auxins, but did not organize root meristems. Auxin-induced cell division was observed in the cambial region within 4 days, and later spread to the outer cortex at the same rate in both tissues. Cells at locations that would normally form roots in foliated hypocotyl cuttings did not produce callus any differently than those in other parts of the cortex. Therefore, auxin-induced root meristem organization appeared to occur independently of auxin-induced cell reorganization/division. The observation that N-(1-naphthyl)phthalamic acid (NPA) promoted cellular reorganization and callus formation but delayed rooting implies the existence of an auxin signal transduction pathway that is specific to root meristem organization. Attempts to induce root formation in callus or explants without foliage were unsuccessful. Both the cotyledon and epicotyl foliage provided a light-dependent product other than auxin that promoted root meristem formation in hypocotyl cuttings.

Journal Article↗
PubMed2001

The relationship between radiologic interpretation and root tip fracture during tooth extraction performed by junior clinicians.

OBJECTIVES: The purpose of this study was to analyze the relationship between root tip fracture and radiologic interpretation of root morphology on periapical radiographs during third molar extraction performed by junior clinicians. METHODS: Before tooth extraction, periapical radiographs of 107 patients with 116 third molars were evaluated by junior clinicians, all with less than 5 years of clinical experience. Radiologic interpretations of root morphology-including number, curvature, fusion, and accessory root-were recorded before each extraction. The clinicians were also asked to estimate the possibility of root fracture on a Visual Analogue Scale before the procedure. The exact morphology of the extracted teeth was recorded after the extraction for the purpose of comparison. RESULTS: Twenty-nine of 116 teeth extracted were not correctly interpreted in at least 1 of the morphologic categories surveyed. The average expected fracture rate of nonfractured teeth was 23.1%, whereas the average expected fracture rate of fractured teeth was a significantly higher 50.3%. Misinterpretation of root morphology on radiographs decreased with increased clinical experience. Senior residents had the lowest misinterpretation and fracture rate. Logistic regression analysis showed that fracture is most closely related to the estimated fracture rate (4.95) and is also significantly related to underestimation of root curvature (0.95; 24.56 with 2 df of chi-square, P = .0001). CONCLUSIONS: Misinterpretation of root morphology on radiographs occurred in 25% of the teeth. Root curvature was the most misinterpreted item studied. Fracture was most closely related to the estimated fracture rate. Junior clinicians in this study expected that only 50% of the fractured teeth would fracture, reflecting a general underestimation of root tip fracture. Further study should be performed to evaluate how to increase the accuracy of root curvature interpretation.

Clinical Competence↗
PubMed2001

Bicuspid aortic valve disease and pulmonary autograft root dilatation after the Ross procedure: a clinicopathologic study.

OBJECTIVE: Bicuspid aortic valve disease has been associated with histologic abnormalities of the aortic root. Recent reports have suggested similar alterations may exist in the pulmonary artery of patients with bicuspid aortic valve. The present study was undertaken to define the histologic condition of the aortic and pulmonary artery root in bicuspid aortic valve disease and the relationship with pulmonary autograft root dilatation after the Ross procedure. METHODS: In 17 patients undergoing aortic root replacement with the pulmonary autograft, biopsy specimens of the aortic root and pulmonary artery trunk were collected. Clinical and histologic findings of patients with bicuspid aortic valves were compared with those with tricuspid aortic valves. RESULTS: There were 9 patients (8 male, 1 female) with bicuspid aortic valve (group 1) and 8 (all male) with tricuspid aortic valve (group 2). Mean age was comparable (24.4 +/- 9.8 vs 23.6 +/- 10.8 years, P =.9). Aortic insufficiency as an indication for operation was more common in group 1 (9/9 vs 5/8, P =.007), whereas preoperative aortic root dilatation was equally prevalent (4/9 vs 1/8, P =.1). Prior aortic valve repair had been performed in 2 patients (1/9 vs 1/8, P =.9). Prevalence of cystic medionecrosis of the aortic wall was similar in the 2 groups (4/9 vs 3/8, P =.6). Cystic medionecrosis of the pulmonary artery trunk was found only in 1 patient with tricuspid aortic valve (0/9 vs 1/8, P =.3). During a mean follow-up of 26.5 +/- 12.2 months (32.1 +/- 12.7 vs 20.1 +/- 7.4 months, P =.04), prevalence of pulmonary autograft root dilatation (greater than 4.0 cm) was equally represented in patients with native bicuspid or tricuspid aortic valve (3/9 vs 2/8, P =.6). CONCLUSIONS: Histologic abnormalities of the pulmonary artery root are rare and equally prevalent in young patients with bicuspid and tricuspid aortic valves. On the contrary, root dilatation is relatively common late after autograft root replacement but appears unrelated to bicuspid aortic valve disease or to pre-existing degenerative changes of the pulmonary artery root.

Adult↗
PubMed2007

Relation of aortic root dilatation and age in Marfan's syndrome.

AIMS: The main aim of this study was to describe the age at which pathological aortic root dilation occurs in patients with Marfan's syndrome (MFS). METHODS AND RESULTS: A total of 160 patients with MFS attending a regional cardiac centre were reviewed retrospectively. Dilation of the ascending aorta was diagnosed by comparing the maximum aortic sinus measurement with control data from the literature. We employed a Kaplan-Meier survival curve to estimate the age at which dilatation occurs. The mean age of the total group at presentation was 15.5 years (range 1.5-40 years). Skeletal abnormalities were present in 95%. Eye involvement was found in 18%. In the 115/160 patients with an abnormal aortic root, 78/115 (68%) developed aortic root dilatation before 19 years of age. From the Kaplan-Meier curve, it can be estimated that about 35% of the patients have aortic root dilatation already at the age of 5 years and 70% before the age of 20 years, and at least 80% by 40 years. There were 31 patients with normal aortic root when first seen but 24/31 (77%) developed aortic root dilatation before the age of 19 years and 7/31 (22.6%) after 19 years of age. Of those (seven patients) who developed new pathological aortic root dilatation after age 19 years, the age range was between 21 and 40 years with a mean of 27 years. Overall, 13 patients (8%) had surgery for aortic root replacement. CONCLUSION: Aortic root dilatation develops early in MFS and was present in 35% by the age of 5 years and 68% by 19 years. Even though new aortic root dilation is relatively rare, it is not possible to safely discharge patients with MFS as about one-third of the patients in our series who developed new pathological aortic root dilation did so after the age of 19 years.

Adolescent↗
PubMed2001

Metabolic inhibition of root water flow in red-osier dogwood (Cornus stolonifera) seedlings.

The short-term effects of sodium azide (NaN(3)) on water flow in red-osier dogwood (Cornus stolonifera Michx.) seedlings were examined in excised roots at a constant pressure of 0.3 MPa. NaN(3) significantly decreased root water flow rates (Q(v)). It also induced a significant reduction in root respiration and reduced stomatal conductance to a greater extent in intact seedlings than in excised shoots. Apoplastic flow of water increased with the NaN(3)-induced decreases in Q(v). Mercuric chloride (HgCl(2)) was also used to characterize the water flow responses and respiration of dogwood roots. Similarly to NaN(3), 0.1 and 0.3 mM HgCl(2) decreased root respiration rates and Q(v). The lower, 0.05 mM HgCl(2) treatment, reduced Q(v), but had no significant effect on root oxygen uptake. The reduction of Q(v) in HgCl(2)-treated plants was only partly reversed by 50 mM mercaptoethanol. The mercurial inhibition of Q(v) suggested the presence of Hg-sensitive water channels in dogwood roots. The results indicate that root-absorbed NaN(3) metabolically inhibited water channel activities in roots and in shoots and resulted in stomatal closure. It is suggested that the inhibition of respiration that occurs in plants stressed with environmental factors such as flooding, cold soils, and drought may be responsible for the closure of water channels in root cells and inhibition of root water flow.

Aquaporins↗
PubMed1995

Influence of environment, fertilizer and genotype on shoot morphology and subsequent rooting of birch cuttings.

Differences in rooting ability of birch (Betula pubescens J.F. Ehrh.) cuttings were observed as a result of differences in genotype and physiology of the stock plants. The uniformity in response among cuttings from micropropagated plants compared with cuttings from seed plants confirmed the advantage of using micropropagated plants to study environmental effects. Shoot morphology of the seed stock plants was influenced by both photoperiod and thermoperiod. A day/night temperature of 15/25 degrees C reduced stem elongation compared with a day/night temperature of 25/15 degrees C regardless of photoperiod, and a continuous light regime resulted in more shoots per plant in both temperature regimes than a 16-h photoperiod. A reduction in the supply of macronutrients did not influence shoot morphology, but increased rooting substantially and seemed to override the effects of environmental factors. In cuttings of seed plants, the highest rooting percentage and number of roots were obtained in a 16-h photoperiod with a day/night temperature of 15/25 degrees C. In micropropagated stock plants, there was a positive correlation between shoot length and number of leaves per shoot and topographical distribution of light within the plants, but there was no correlation between these parameters and rooting ability of the cuttings. A rooting temperature of 16 degrees C delayed the rate of root production compared with the rate at higher temperatures, but the final rooting percentage was the same over the range from 16 to 28 degrees C. Root branching increased with temperature. At all temperatures, there was a large increase in sucrose content at the base of the cuttings during rooting, whereas the concentration of nontranslocated sugars remained constant. The carbohydrate content at the base of cuttings from micropropagated stock plants was three times higher than at the base of cuttings from seed stock plants, but the higher carbohydrate content was not correlated with a higher rooting potential.

Journal Article↗
PubMedDate not supplied

Effects of elevated CO(2) and nitrogen on the synchrony of shoot and root growth in ponderosa pine.

We monitored effects of elevated CO(2) and N fertilization on shoot and fine root growth of Pinus ponderosa Dougl. ex P. Laws. and C. Laws. grown in native soil in open-top field-exposure chambers at Placerville, CA, over a 2-year period. The experimental design was a replicated 3 x 3 factorial with the center treatment missing; plants were exposed to ambient (~365 micro mol mol(-1)) air or ambient air plus either 175 or 350 micro mol mol(-1) CO(2) in combination with one of three rates of N addition (0, 100 or 200 kg ha(-1) year(-1)). All CO(2) by N interactions were nonsignificant. Both the CO(2) and N treatments increased plant height, stem diameter and leaf area index (LAI). Elevated CO(2) increased fine root area density and the occurrence of mycorrhizae, whereas N fertilization increased coarse root area density but had no effect on fine root area density. Spring flushes of shoot height and diameter growth were initiated concurrently with the increase in new root area density but height and diameter growth reached their maxima before that of fine roots. The temporal patterns of root and shoot growth were not altered by providing additional CO(2) or N. Greatest root loss occurred in the summer, immediately following the period of greatest new fine root growth. Elevated N initially reduced the fine root area density/LAI ratio independently of CO(2) treatment, indicating that the relationship between fine roots and needles was not changed by CO(2) exposure.

Journal Article↗
PubMedDate not supplied

Effects of CO(2) enrichment on growth and root (15)NH(4) (+) uptake rate of loblolly pine and ponderosa pine seedlings.

We examined changes in root growth and (15)NH(4) (+) uptake capacity of loblolly pine (Pinus taeda L.) and ponderosa pine (Pinus ponderosa Douglas. Ex Laws.) seedlings that were grown in pots in a phytotron at CO(2) partial pressures of 35 or 70 Pa with NH(4) (+) as the sole N source. Kinetics of (15)N-labeled NH(4) (+) uptake were determined in excised roots, whereas total NH(4) (+) uptake and uptake rates were determined in intact root systems following a 48-h labeling of intact seedlings with (15)N. In both species, the elevated CO(2) treatment caused a significant downregulation of (15)NH(4) (+) uptake capacity in excised roots as a result of a severe inhibition of the maximum rate of root (15)NH(4) (+) uptake (V(max)). Rates of (15)NH(4) (+) uptake in intact roots were, however, unaffected by CO(2) treatment and were on average 4- to 10-fold less than the V(max) in excised roots, suggesting that (15)NH(4) (+) absorption from the soil was not limited by the kinetics of root (15)NH(4) (+) uptake. Despite the lack of a CO(2) effect on intact root absorption rates, (15)NH(4) (+) uptake on a per plant basis was enhanced at high CO(2) concentrations in both species, with the relative increase being markedly higher in ponderosa pine than in loblolly pine. High CO(2) concentration increased total (15)NH(4) (+) uptake and the fraction of total biomass allocated to fine roots (< 2 mm in diameter) to a similar relative extent. We suggest that the increased uptake on a per plant basis in response to CO(2) enrichment is largely the result of a compensatory increase in root absorbing surfaces.

Journal Article↗
PubMed1999

Can differences in root responses to soil drying and compaction explain differences in performance of trees growing on landfill sites?

Two tropical woody species, Acacia confusa Merrill and Litsea glutinosa (Lour.) C.B. Robinson, were grown under controlled conditions in PVC pipes filled with John Innes No. 2 soil. To investigate root distribution, physiological characteristics and hydraulic conductivity, four soil treatments were imposed-well-watered and noncompacted (control), well-watered and compacted; unwatered and noncompacted, and unwatered and compacted. In L. glutinosa, rooting depth and root elongation were severely restricted when soil bulk density increased from around 1.12 to 1.62 g cm(-3), whereas soil compaction had little effect on these parameters in A. confusa. As soil drying progressed, root water potential and osmotic potential declined more slowly in L. glutinosa than in A. confusa. Both the soil drying and compaction treatments significantly stimulated the accumulation of root abscisic acid (ABA) in both species. Soil drying damaged the root cell membrane of A. confusa, but had little influence on the root cell membrane of L. glutinosa. Soil drying had a greater effect on root hydraulic conductivity (L(p)) in L. glutinosa than in A. confusa, whereas the effect of soil compaction on L(p) was less in L. glutinosa than in A. confusa. Soil drying enhanced the effects of soil compaction on root L(p). We conclude that soil drying and compaction have large species-specific effects on the distribution, growth and physiology of roots. The relationships of these root properties to the species' ability to tolerate unfavorable soil conditions were examined.

Journal Article↗
PubMed1987

A semi-automated data processing system for root growth analysis: application to a growing oak seedling.

A data acquisition and processing system for analyzing root structure and growth is presented. Two-dimensional drawings are made of root systems growing against the inclined, transparent wall of a rhizotron. For analysis, a root is treated as a number of straight segments between points determined by the position of root apices at successive times of observation and the insertion points of lateral roots. The coordinates of the points are digitized by means of a graphics tablet and the description of the root system completed with information about root branching pattern and root order. From the recorded data, various root characteristics and growth parameters can be computed with a program available from the authors. Use of the data processing system in studies of root architecture is discussed and its application in the analysis of root growth of a pedunculate oak seedling (Quercus robur L.) reported.

Journal Article↗
PubMed1988

Effects of hypoxia and elevated carbon dioxide concentration on water flux through Populus roots.

Restricted gas exchange between the rhizosphere and aerial environment reduces the concentration of oxygen (O(2)) and elevates the concentration of carbon dioxide (CO(2)) in the root zone, thereby leading to increased resistance to root water uptake. In this study, the effects of hypoxia and 20% CO(2) on water flux (J(v)) through roots of hybrid poplar (Populus trichocarpa Torr. & A. Gray x P. deltoides Bartr. ex Marsh) were measured in detached root systems under pressure in solution culture. Because stomata closed and there was no change in foliar water potential in hypoxic plants, root resistance was measured in detached systems as opposed to using whole plant measurements. However, under aerated conditions root resistance values were similar in intact plants and excised roots. Water fluxes through pressurized root systems treated with nitrogen and low oxygen (< 2% O(2)), elevated CO(2) (20% CO(2)), and low O(2) with elevated CO(2) concentrations were reduced to 40, 51 and 58%, respectively, of J(v) of plants aerated with ambient air. Reductions in J(v) occurred more rapidly in response to elevated CO(2) than to low O(2) concentrations. The effects of low O(2) and elevated CO(2) were not additive. Changes in pH that resulted from elevated CO(2) concentrations did not account for the reduction in J(v). When root systems of intact plants were pretreated for 24 or 48 h with low O(2) concentration, J(v) measured on pressurization was reduced by 33 and 48%, respectively, compared to aerated roots. Stomatal conductance was also reduced, however, so leaf water potential of plants with hypoxic roots were similar to those of aerated controls.

Journal Article↗