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At least 127 records · Page 7Linked to original sources
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↗
PubMed2003

[Roles of rhizosphere in remediation of contaminated soils and its mechanisms].

Rhizosphere is a special 'ecological remediation unit' to treat contaminated soils, which contains a great quantity of microorganisms such as fungi and rhizobacteria living with plant roots. Thus, physiological and ecological roles of plant roots to remedy contaminated soils, to accumulate and to solidify heavy metals, to absorb and degrade organic pollutants in rhizosphere were illustrated, and the function of mycorrhizospheric fungi to absorb, barrier and chelate heavy metals, to degrade organic pollutants through their metabolism activities, the action of rhizobacteria to absorb and solidify heavy metals, to degrade organic pollutants in rhizosphere through their active living activities, and the combined remediation of fungi and bacteria to pollutants in rhizosphere and their relevant mechanisms were explained. It was suggested that the remediation role of rhizosphere was the main part of phytoremediation, and one of the main basic theories to remedy contaminated soils by the activity of green plants and other organisms. The use of hyperaccumulative plants in remedying soils contaminated by some heavy metals would be prospective. It would be one of the important approach to contaminated soils remediation by organic pollutants through the mechanism of screening some special plants whose roots had strong secreting ability to absorb and accumulate dissolvent organic pollutants on the basis of inoculating specific or non-specific fungi and bacteria from the rhizosphere. This will be a developing trend of research on the remediation of contaminated soils by organic pollutants.

Bacteria↗
PubMed2000

ASTROCULTURE (TM) root metabolism and cytochemical analysis.

Physiology of the root system is dependent upon oxygen availability and tissue respiration. During hypoxia nutrient and water acquisition may be inhibited, thus affecting the overall biochemical and physiological status of the plant. For the Astroculture (TM) plant growth hardware, the availability of oxygen in the root zone was measured by examining the changes in alcohol dehydrogenase (ADH) activity within the root tissue. ADH activity is a sensitive biochemical indicator of hypoxic conditions in plants and was measured in both spaceflight and control roots. In addition to the biochemical enzyme assays, localization of ADH in the root tissue was examined cytochemically. The results of these analyses showed that ADH activity increased significantly as a result of spaceflight exposure. Enzyme activity increased 248% to 304% in dwarf wheat when compared with the ground controls and Brassica showed increases between 334% and 579% when compared with day zero controls. Cytochemical staining revealed no differences in ADH tissue localization in any of the dwarf wheat treatments. These results show the importance of considering root system oxygenation in designing and building nutrient delivery hardware for spaceflight plant cultivation and confirm previous reports of an ADH response associated with spaceflight exposure.

Alcohol Dehydrogenase↗
PubMed1996

Localization of glycosaminoglycans in periodontal ligament during physiological and experimental tooth movement.

Localization of chondroitin sulphates in periodontal ligaments (PDL) of rat molar roots during physiological and experimental tooth movement were analysed immunohistochemically with the use of monoclonal antibodies, 3B3 and 2B6, specific to chondroitin 6-sulphate (CH-6S) and chondroitin 4-sulphate/dermatan sulfate (CH-4S/DS), respectively. The maxillary first molars of experimental animals were forced to move laterally with a 10 g weight by U-shaped wires for 3 and 7 d. In control animals, 3B3 epitope was seen in the PDL near to the bone surface facing the distal half of roots, which corresponded to the compressive side during physiological tooth movement. Immunoreactivity for 2B6 was weak or negative in the PDL. Both epitopes were present at osteoid, precementum, lacunae and canaliculli of osteocytes and cementocytes. In 3-d-treated animals, the early stage of hyalinization characterized with visible cells and fibres was observed in the PDL at the buccal side of the mesial root, which showed intense immunoreactivity for 3B3. Further 3B3 positive area seen in control animals changed its position from the distal to the buccal side of the PDL. Immunoreactivity for 2B6 did not change in the PDL of 3-d-treated animals. In 7-d-treated animals, the typical hyalinization characterized with no visible cells and fibres was seen in the PDL at the buccal sides of both mesial and disto-buccal roots, where both epitopes were present at the peripheral part of the tissue. Observation of serial sections suggested that the 3B3-positive area was present at the peripheral part of the 2B6-positive area. The present results suggest that the expression of CH-6S is related to the compressive force in non-hyalinized and hyalinized PDL, whereas that of CH-4S/DS is not influenced by the mechanical stress.

Alveolar Process↗
PubMed2006

A central role for the nitrate transporter NRT2.1 in the integrated morphological and physiological responses of the root system to nitrogen limitation in Arabidopsis.

Up-regulation of the high-affinity transport system (HATS) for NO(3)(-) and stimulation of lateral root (LR) growth are two important adaptive responses of the root system to nitrogen limitation. Up-regulation of the NO(3)(-) HATS by nitrogen starvation is suppressed in the atnrt2.1-1 mutant of Arabidopsis (Arabidopsis thaliana), deleted for both NRT2.1 and NRT2.2 nitrate transporter genes. We then used this mutant to determine whether lack of HATS stimulation affected the response of the root system architecture (RSA) to low NO(3)(-) availability. In Wassilewskija (Ws) wild-type plants, transfer from high to low NO(3)(-) medium resulted in contrasting responses of RSA, depending on the level of nitrogen limitation. Moderate nitrogen limitation (transfer from 10 mm to 1 or 0.5 mm NO(3)(-)) mostly led to an increase in the number of visible laterals, while severe nitrogen stress (transfer from 10 mm to 0.1 or 0.05 mm NO(3)(-)) promoted mean LR length. The RSA response of the atnrt2.1-1 mutant to low NO(3)(-) was markedly different. After transfer from 10 to 0.5 mm NO(3)(-), the stimulated appearance of LRs was abolished in atnrt2.1-1 plants, whereas the increase in mean LR length was much more pronounced than in Ws. These modifications of RSA mimicked those of Ws plants subjected to severe nitrogen stress and could be fully explained by the lowered NO(3)(-) uptake measured in the mutant. This suggests that the uptake rate of NO(3)(-), rather than its external concentration, is the key factor triggering the observed changes in RSA. However, the mutation of NRT2.1 was also found to inhibit initiation of LR primordia in plants subjected to nitrogen limitation independently of the rate of NO(3)(-) uptake by the whole root system and even of the presence of added NO(3)(-) in the external medium. This indicates a direct stimulatory role for NRT2.1 in this particular step of LR development. Thus, it is concluded that NRT2.1 has a key dual function in coordinating root development with external NO(3)(-) availability, both indirectly through its role as a major NO(3)(-) uptake system that determines the nitrogen uptake-dependent RSA responses, and directly through a specific action on LR initiation under nitrogen-limited conditions.

Anion Transport Proteins↗
PubMed1983

Proteolytic Activity in Soybean Root Nodules : Activity in Host Cell Cytosol and Bacteroids throughout Physiological Development and Senescence.

Root nodules were harvested from chamber-grown soybean (Glycine max L. Merrill cv Woodworth) plants throughout development. Apparent nitrogenase activity (acetylene reduction) peaked before seeds began to develop, but a significant amount of activity remained as the seeds matured. Nodule senescence was defined as the period in which residual nitrogenase activity was lost. During this time, soluble protein and leghemoglobin levels in the host cell cytosol decreased, and proteolytic activity against azocasein increased. Degradative changes were not detected in bacteroids during nodule senescence. Total soluble bacteroid protein per gram of nodule remained constant, and an increase in proteolytic activity in bacteroid extracts was not observed. These results are consistent with the view that soybean nodule bacteroids are capable of redifferentiation into free-living bacteria upon deterioration of the legume-rhizobia symbiosis.

Journal Article↗
PubMed1994

Localization of uncalcified cementum in adult rat molar roots and its relation to physiological tooth movement.

The study was designed to elucidate the effect of physiological tooth movement on cellular cementum, using the upper molar roots of 10-week-old rats. Paraffin sections stained with haematoxylin and eosin displayed two types of cellular cementum, lightly and darkly staining. The lightly stained was present on the distal half of all molar roots except the mesial root of the first molar. The alveolar bone facing the lightly stained cementum showed resorption lacunae and multinucleated osteoclasts, while the opposite bone surface was lined with osteoblasts. In contact microradiographs of undemineralized ground sections, the X-ray density of the lightly stained cementum was similar to that of the periodontal ligament and pulp, while the X-ray density of the darkly stained cementum was similar to that of alveolar bone. Tetracycline labelling lines were seen at the interface between the two types of cellular cementum as well as on surfaces of bone and cementum located mesially to the root dentine. The results suggest that the mechanical stress of tooth movement differently affects the alveolar bone and cellular cementum; the bone is resorbed whereas the cementum resists resorption and its calcification is inhibited under the compressive force of tooth movement.

Absorptiometry, Photon↗
PubMed2004

Physiologically mediated self/non-self discrimination in roots.

Recent evidence suggests that self/non-self discrimination exists among roots; its mechanisms, however, are still unclear. We compared the growth of Buchloe dactyloides cuttings that were grown in the presence of neighbors that belonged to the same physiological individual, were separated from each other for variable periods, or originated from adjacent or remote tillers on the same clone. The results demonstrate that B. dactyloides plants are able to differentiate between self and non-self neighbors and develop fewer and shorter roots in the presence of other roots of the same individual. Furthermore, once cuttings that originate from the very same node are separated, they become progressively alienated from each other and eventually relate to each other as genetically alien plants. The results suggest that the observed self/non-self discrimination is mediated by physiological coordination among roots that developed on the same plant rather than allogenetic recognition. The observed physiological coordination is based on an as yet unknown mechanism and has important ecological implications, because it allows the avoidance of competition with self and the allocation of greater resources to alternative functions.

Plant Roots↗
PubMed1992

The anchoring strengths of various chest hair root types.

The force required to epilate single chest hairs was measured electronically during a slow (0.09 m/s) machine-driven extraction. Telogen hairs showed a mean anchoring strength of 70 g (s.d. = 16). Anagen hairs, with variable amounts of surrounding root sheaths, had a mean of 71 g (s.d. = 10) whereas bare anagen hairs had a mean of 66 g (s.d. = 13). The catagen phase had a mean of 62 g (s.d. = 8). It is highly likely that the anchoring mechanisms of anagen and telogen roots are as different physiologically as these roots are different anatomically yet both are sufficiently strong to resist the ordinary tractions and pullings to which hair is subject.

Biomechanical Phenomena↗
PubMed2000

Physiological aspects of fungi isolated from root nodules of faba bean (Vicia faba L.).

The present study was made to isolate and assess some physiological characteristics of root nodule-colonizing fungi. During this study, 17 fungal species were isolated from root nodule samples taken from faba bean plants (Vicia faba L.) collected from different sites at Assiut area (Egypt). The growth of faba bean plants in pots was significantly promoted by soil inoculation with most fungi. Growth was checked in pots with inocula of Cladosporium cladosporioides, Fusarium moniliforme, F: oxysporium, F solani, Macrophominia phaseolina and Rhizoctonia solani which were added separately. All growth-promoting fungi were capable of producing cellulase, pectin lyase, polygalacturonase, protease, urease, amidase, acid phosphatase, alkaline phosphatase and arylsulfatase in growth medium supplemented with the corresponding substrates. Four fungal species, Aspergillus awamori, A. flavus, Penicillium chrysogenum and Trichoderma koningii showed the highest rates of enzyme formation. The effect of the addition of six trace elements to the growth media at 30 micromol/ml on enzyme production revealed some dependency on species, enzyme and metal ion. Cd2+, Hg2+ and Zn2+ generally inhibited enzyme activity. Cu(1+), Fe3+ and Al3+ showed a stimulatory effect. Fungicides (afugan and tilt) and herbicides (brominal and fusilade) at 50 ppm generally promoted enzyme activity, but insecticides (kelthane and fenvalerate) caused some inhibition to enzyme activities. Salinization of the growth media with NaCl strongly inhibited the enzymatic activity of all fungi at concentrations between 0.5 and 1.5%.

Fabaceae↗
PubMed1991

Unique microvascular characteristics of the dorsal root ganglion in the rat.

Physiological characteristics of dorsal root ganglia microvessels have not been reported in detail. In this study we examined local blood flow and oxygen tension in the L4 dorsal root ganglion (DRG) of the rat. Under normal physiological conditions, local DRG blood flow measured 36.1 +/- 2.7 ml/100 g/min, over twice that within the endoneurium of the sciatic nerve. DRG blood flow was better maintained during hypotension than endoneurial blood flow suggesting partial autoregulation. Unlike endoneurium, there was relative constancy of flow between mean arterial pressures of 60 and 120 mm Hg. Hypercarbia with acidosis, and hypocarbia with alkalosis did not influence blood flow. The histogram of oxygen tensions within the dorsal root ganglion resembled that in brain but included more values at lower tensions than observed in published endoneurial histograms. Theses findings suggest that the DRG differ from endoneurium in ways that reflect the higher metabolic requirements of neural soma.

Acidosis↗
PubMed2005

Ascending migration of endophytic rhizobia, from roots to leaves, inside rice plants and assessment of benefits to rice growth physiology.

Rhizobia, the root-nodule endosymbionts of leguminous plants, also form natural endophytic associations with roots of important cereal plants. Despite its widespread occurrence, much remains unknown about colonization of cereals by rhizobia. We examined the infection, dissemination, and colonization of healthy rice plant tissues by four species of gfp-tagged rhizobia and their influence on the growth physiology of rice. The results indicated a dynamic infection process beginning with surface colonization of the rhizoplane (especially at lateral root emergence), followed by endophytic colonization within roots, and then ascending endophytic migration into the stem base, leaf sheath, and leaves where they developed high populations. In situ CMEIAS image analysis indicated local endophytic population densities reaching as high as 9 x 10(10) rhizobia per cm3 of infected host tissues, whereas plating experiments indicated rapid, transient or persistent growth depending on the rhizobial strain and rice tissue examined. Rice plants inoculated with certain test strains of gfp-tagged rhizobia produced significantly higher root and shoot biomass; increased their photosynthetic rate, stomatal conductance, transpiration velocity, water utilization efficiency, and flag leaf area (considered to possess the highest photosynthetic activity); and accumulated higher levels of indoleacetic acid and gibberellin growth-regulating phytohormones. Considered collectively, the results indicate that this endophytic plant-bacterium association is far more inclusive, invasive, and dynamic than previously thought, including dissemination in both below-ground and above-ground tissues and enhancement of growth physiology by several rhizobial species, therefore heightening its interest and potential value as a biofertilizer strategy for sustainable agriculture to produce the world's most important cereal crops.

Colony Count, Microbial↗
PubMed2006

Photoperiodic regulation in energy intake, thermogenesis and body mass in root voles (Microtus oeconomus).

The present study was designed to examine whether photoperiod alone was effective to induce seasonal regulations in physiology in root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau noted for its extreme cold environment. Root voles were randomly assigned into either long photoperiod (LD; 16L:8D) or short photoperiod (SD; 8L:16D) for 4 weeks at constant temperature (20 degrees C). At the end of acclimation, SD voles showed lower body mass and body fat coupled with higher energy intake than LD voles. SD greatly enhanced thermogenic capacities in root voles, as indicated by elevated basal metabolic rate (BMR), nonshivering thermogenesis (NST), mitochondrial protein content and uncoupling protein-1 (UCP1) content in brown adipose tissue (BAT). Although no variations in serum leptin levels were found between SD and LD voles, serum leptin levels were positively correlated with body mass and body fat mass, and negatively correlated with energy intake and UCP1 content in BAT, respectively. To summarize, SD alone is effective in inducing higher thermogenic capacities and energy intake coupled with lower body mass and body fat mass in root voles. Leptin is potentially involved in the photoperiod induced body mass regulation and thermogenesis in root voles.

Adipose Tissue↗
PubMed1992

[Spinal neurons activated by ventral root afferents in rats: their physiological properties, distribution in the spinal cord and rostral projection].

The present experiment was designed to locate spinal neurons which are activated by afferent fibers in the ventral roots, and once found, to study their receptive field and rostral projection. After dorsal roots L1 approximately S4 on the left side were cut under a binocular microscope, stimulus was applied to ventral roots and extracellular responses were recorded using a glass microelectrode filled with fast green FCF. Sixty-four neurons were activated by stimulating ventral roots at 1.2-27.8 x T of the lowest threshold fibers of the ventral root. Six neurons were classified as wide dynamic neurons and 29 as high threshold neurons according to their response patterns to the periphery. Twelve neurons out of 29 were unresponsive to cutaneous stimulation, and located lamina V, suggesting that they innervate visceral organs. Thirty-five neurons (54.6%) were nociceptive nerons, most of which were located in laminae V and VI. In 6 neurons out of 35 nociceptive neurons (17.1%), rostral projection was confirmed by the collision block method and the ability to respond to high frequency stimuli with constant latency. Our results suggest that some spinal neurons activated primary affernt fibers in ventral roots stimulation are nociceptive and some of them are rostral projecting neurons which are antidromically activated ventral quadrants of the spinal cord.

Action Potentials↗