PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Root physiology”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources
PubMed1999

Multiple idiopathic resorption in the primary dentition: review of the literature and case report.

Resorption of primary teeth is a normal physiologic process, except when it occurs prematurely. Resorption of permanent teeth is considered abnormal, and multiple etiologic factors have been implicated. A significant number of cases are represented by idiopathic resorption. Multiple idiopathic root resorption stands as a separate physiologic entity that has been described as affecting the entire permanent dentition. Multiple idiopathic resorption of primary teeth has not been previously reported. A case is described and a differential diagnosis is provided. The specific radiographic diagnostic criteria for this condition affecting the primary dentition are outlined.

Child↗
PubMed1996

Characterization of a calcium/calmodulin-dependent protein kinase homolog from maize roots showing light-regulated gravitropism.

Roots of many species respond to gravity (gravitropism) and grow downward only if illuminated. This light-regulated root gravitropism is phytochrome-dependent, mediated by calcium, and inhibited by KN-93, a specific inhibitor of calcium/calmodulin-dependent protein kinase II (CaMK II). A cDNA encoding MCK1, a maize homolog of mammalian CaMK, has been isolated from roots of maize (Zea mays L.). The MCK1 gene is expressed in root tips, the site of perception for both light and gravity. Using the [35S]CaM gel-overlay assay we showed that calmodulin-binding activity of the MCK1 is abolished by 50 microM KN-93, but binding is not affected by 5 microM KN-93, paralleling physiological findings that light-regulated root gravitropism is inhibited by 50 microM KN-93, but not by 5 microM KN-93. KN-93 inhibits light-regulated gravitropism by interrupting transduction of the light signal, not light perception, suggesting that MCK1 may play a role in transducing light. This is the first report suggesting a physiological function for a CaMK homolog in light signal transduction.

Amino Acid Sequence↗
PubMed1990

Proteolysis is a critical step in the physiological stop pathway: mechanisms involved in the blockade of axonal regeneration by mammalian astrocytes.

Regenerating axons of adult dorsal roots are stopped by reactive astrocytes at the PNS-CNS junction. While it has been suggested that the astrocytes might pose a physical barrier to axonal growth, based on ultrastructural comparisons of physically blocked and axo-glial endings, it was proposed that astrocytes in the root transitional zone block axonal growth by activating the physiological stop pathway within the growing axon tips. Part of the stop pathway involves the proteolytic breakdown and removal of neurofilaments as they enter the axon endings. Another component involves the establishment of anterograde-to-retrograde conversion for the removal of membranous elements from the axonal endings. Both of these components appear to be dependent upon the activation of proteases within the axon tips. Therefore, to further test our hypothesis we infused, by intrathecal catheterization, the region of the dorsal root transitional zone with the protease inhibitor leupeptin at a time when the majority of regenerating axons have terminated in the region. Ultrastructural analyses after leupeptin treatment revealed axo-glial endings distended by accumulations of neurofilaments and organelles, particularly tubulovesicular profiles. These observations further support the idea that astrocytes, like normal target cells, can activate the physiological stop pathway.

Animals↗
PubMed2005

Moving with the flow: what transport laws reveal about cell division and expansion.

This material was presented as a keynote talk for the symposium, "Crosstalk between cell division and expansion," organized by G.T.S. Beemster and H. Tsukaya at the International Botanical Congress, Vienna in July, 2005. The review focuses on the utility of continuity equations to understand relationships among cell size, division and expansion; insights from Lagrangian or cell-specific descriptions of developmental variables; and a growth-diffusion equation to show effects of root growth zones on the surrounding soil.

Biomechanical Phenomena↗
PubMed2005

Root functioning modifies seasonal climate.

Hydraulic redistribution (HR), the nocturnal vertical transfer of soil water from moister to drier regions in the soil profile by roots, has now been observed in Amazonian trees. We have incorporated HR into an atmospheric general circulation model (the National Center for Atmospheric Research Community Atmospheric Model Version 2) to estimate its impact on climate over the Amazon and other parts of the globe where plants displaying HR occur. Model results show that photosynthesis and evapotranspiration increase significantly in the Amazon during the dry season when plants are allowed to redistribute soil water. Plants draw water up and deposit it into the surface layers, and this water subsidy sustains transpiration at rates that deep roots alone cannot accomplish. The water used for dry season transpiration is from the deep storage layers in the soil, recharged during the previous wet season. We estimate that HR increases dry season (July to November) transpiration by approximately 40% over the Amazon. Our model also indicates that such an increase in transpiration over the Amazon and other drought-stressed regions affects the seasonal cycles of temperature through changes in latent heat, thereby establishing a direct link between plant root functioning and climate.

Atmosphere↗
PubMed1996

Electro-optical imaging of F-actin and endoplasmic reticulum in living and fixed plant cells.

Confocal and video micrographs of living and fixed alfalfa roots, onion epithelial and pear pollen cells illustrate the architecture of the cytoskeleton and endoplasmic reticulum in plant cells. Fixation of plant tissues to preserve cytoplasmic structure poses special problems. When possible, emphasis should be placed on the imaging of structures in stained living cells over time. The early events that occur when Nod factors or bacteria elicit nodule formation in alfalfa roots will illustrate several approaches to plant cell fixation, staining and imaging. The first observable events after Nod factor stimulation occur in root hairs and are changes in rates of cytoplasmic streaming, nuclear movements, and changes in the shape of the vacuole. Within ten minutes, the endoplasmic reticulum shifts position towards the tip of the root hair. For comparison, the endoplasmic reticulum localization in pollen tubes and onion epithelial cells will be illustrated. The actin cytoskeleton undergoes a series of changes over a twelve hour period. These changes in the cytoskeleton are spatially and temporally correlated with the observed growth changes of the root hairs. This dynamic change of the actin filament and endoplasmic reticulum and associated secretory vesicles in these root hairs suggests a mechanism for the observed root hair growth changes.

Actins↗
PubMed2006

Towards the elucidation of AM-specific transcription in Medicago truncatula.

Roots of most plants form a mutualistic interaction with arbuscular mycorrhiza (AM) fungi. During the symbiosis, drastic morphological and physiological changes occur in the host plant root system. These changes are likely to be controlled by a specific genetic program of the plant. The legume Medicago truncatula is a model system widely used to elucidate this program. A number of loci required for AM-development have been identified by the analysis of M. truncatula mutants; however, the genes identified are also required for the Legume-Rhizobium symbiosis, since all M. truncatula mycorrhizal mutants so far reported are also nodulation mutants. We have focused on the identification and analysis of AM-specific genes as a further means to gain insight into the molecular background of the AM symbiosis and the molecular regulation of this tight symbiosis. Here, we describe the identification of AM-specific genes and the analysis of their transcriptional regulation. The identification of promoters and regulatory elements mediating the mycorrhiza-specific transcription provides a starting point to identify the corresponding specific transcription factors. This enables the identification of further upstream elements of the regulation cascade, and thus the elucidation of the molecular mechanisms controlling the AM-development within plant roots.

Gene Expression Regulation, Plant↗
PubMed2004

Effects of inoculum conditions on growth of hairy roots of Panax ginseng C.A. Meyer.

Plants have a potential to produce a large number of important metabolites such as pharmaceuticals, food additives, pigments, flavors, fragrances, and fine chemicals. Large-scale plant cell and tissue cultures for producing useful products has been considered an attractive alternative to whole plant extraction for obtaining valuable chemicals. In plant cell and tissue cultures, cell growth and metabolite production are influenced by nutritional and environmental conditions as well as physical properties of the culture system. To obtain a high growth rate of plant cell and tissue cultures, the culture conditions should be maintained at an optimum level. We studied the relationship between inoculum conditions and the growth of Panax ginseng hairy root culture, and found that the growth rate varied with the inoculum conditions such as the number of root tips, the length of root tips, the part of root tips, and the inoculum size and age of hairy roots.

Biotechnology↗
PubMed1996

[The interaction of a root growing vertically with a rigid barrier].

Bending root tip that grows outside the soil is investigated. The decrease of growth rate due to increasing compressive stress leads to the destabilization of uniform solution, whereas differential growth that is controlled by root cap gravitropism is a stabilizing factor. The interplay of both processes leads to diverse behaviour types.

Gravitropism↗
PubMed1999

Nitrate regulation of metabolism and growth.

Recent research shows that signals derived from nitrate are involved in triggering widespread changes in gene expression, resulting in a reprogramming of nitrogen and carbon metabolism to facilitate the uptake and assimilation of nitrate, and to initiate accompanying changes in carbon metabolism. These nitrate-derived signals interact with signals generated further downstream in nitrogen metabolism, and in carbon metabolism. Signals derived from internal and external nitrate also adjust root growth and architecture to the physiological state of the plant, and the distribution of nitrate in the environment.

Fungi↗
PubMed1987

The role of calcium ions in gravity signal perception and transduction.

Ca2+ is implicated as a messenger in coupling various environmental stimuli, such as gravity and light, to response. In recent years, it has become evident that Ca2+ plays a central role in all three phases of gravitropism--perception, transduction and response. The root cap, which is known to contain high amounts of Ca2+ and calmodulin, is the primary site of gravity perception. The possible role of phosphoinositide turnover and Ca(2+) - and Ca(2+) -calmodulin-dependent enzymes such as Ca(2+) -ATPase and protein kinases in gravitropism is discussed. A model is proposed to describe the role of Ca2+ in both normal and light-dependent gravity response in roots.

Calcium↗
PubMed2003

Molecular and physiological characterization of Italian isolates of Pyrenochaeta lycopersici.

Corky root of tomato caused by Pyrenochaeta lycopersici is a disease of concern in Italy and for many tomato growing areas in the world. Isolates of the fungus were characterized at both the physiological and molecular level. The optimal in vitro growth temperature for all isolates was 23 degrees C. All Italian isolates of P. lycopersici showed similar RAPD and esterase banding patterns. No relevant polymorphisms were detected after enzymatic digestion of PCR-amplified ITS and IGS regions. The overall results indicate a low degree of genetic variability within a collection of 43 Italian isolates. These data are of interest in breeding programs for resistance against corky root of tomato and they provide useful information for the development of molecular diagnostic tools for the rapid identification and detection of P. lycopersici.

DNA, Fungal↗
PubMed1996

The Physiological Relevance of Na+-Coupled K+-Transport.

Plant roots utilize at least two distinct pathways with high and low affinities to accumulate K+. The system for high-affinity K+ uptake, which takes place against the electrochemical K+ gradient, requires direct energization. Energization of K+ uptake via Na+ coupling has been observed in algae and was recently proposed as a mechanism for K+ uptake in wheat (Triticum aestivum L.). To investigate whether Na+ coupling has general physiological relevance in energizing K+ transport, we screened a number of species, including Arabidopsis thaliana L. Heynh. ecotype Columbia, wheat, and barley (Hordeum vulgare L.), for the presence of Na+-coupled K+ uptake. Rb+-flux analysis and electrophysiological K+-transport assays were performed in the presence and absence of Na+ and provided evidence for a coupling between K+ and Na+ transport in several aquatic species. However, all investigated terrestrial species were able to sustain growth and K+ uptake in the absence of Na+. Furthermore, the addition of Na+ was either without effect or inhibited K+ absorption. The latter characteristic was independent of growth conditions with respect to Na+ status and pH. Our results suggest that in terrestrial species Na+-coupled K+ transport has no or limited physiological relevance, whereas in certain aquatic angiosperms and algae this type of secondary transport energization plays a significant role.

Journal Article↗
PubMed2002

A four-dimensional study of the aortic root dynamics.

OBJECTIVE: Although aortic root expansion has been well studied, its deformation and physiologic relevance remain controversial. Three-dimensional (3-D) sonomicrometry (200Hz) has made time-related 4-D study possible. METHODS: Fifteen sonomicrometric crystals were implanted into the aortic root of eight sheep at each base (three), commissures (three), sinuses of Valsalva (three), sinotubular junction (three), and ascending aorta (three). In this acute, open-chest model, the aortic root geometric deformations were time related to left ventricular and aortic pressures. RESULTS: During the cardiac cycle, aortic root volume increased by mean+/-1 standard error of the mean (SEM) 33.7+/-2.7%, with 36.7+/-3.3% occurring prior to ejection. Expansion started during isovolumic contraction at the base and commissures followed (after a delay) by the sinotubular junction. At the same time, ascending aorta area decreased (-2.6+/-0.4%). During the first third of ejection, the aortic root reached maximal expansion followed by a slow, then late rapid decrease in volume until mid-diastole. During end-diastole, the aortic root volume re-expanded by 11.3+/-2.4%, but with different dynamics at each area level. Although the base and commissural areas re-expanded, the sinotubular junction and ascending aorta areas kept decreasing. At end-diastole, the aortic root had a truncated cone shape (base area>commissures area by 51.6+/-2.0%). During systole, the root became more cylindrical (base area>commissures area by 39.2+/-2.5%) because most of the significant changes occurred at commissural level (63.7+/-3.6%). CONCLUSION: Aortic root expansion follows a precise chronology during systole and becomes more cylindrical - probably to maximize ejection. These findings might stimulate a more physiologic approach to aortic valve and aortic root surgical procedures.

Animals↗
PubMed1983

Morphological and physiological characteristics and lipopolysaccharide composition of N2-fixing (C2H2-reducing) root-associated Pseudomonas sp.

A dinitrogen-fixing Pseudomonas sp. was isolated from the roots of the grass Deschampsia caespitosa. The motile organism, which had 4 to 10 polar flagella, was gram negative, obligately aerobic, oxidase positive, arginine dihydrolase positive, and fluorescent. To verify API20B, API20E, and Oxi-Ferm identifications, as well as results from standard microbiological tests and electron microscopic examinations, which all indicated the organism to be a Pseudomonas, we analyzed its lipopolysaccharide. The lipopolysaccharide contained neutral sugars, phosphorus, heptose, hexosamine, 2-keto-3-deoxyoctonate, and fatty acids, which were dodecanoic, 3-hydroxydecanoic, 2-hydroxydodecanoic, and 3-hydroxydodecanoic acids. Both the qualitative and quantitative compositions resembled known data of the genus Pseudomonas. Dinitrogen fixation, determined as C2H2 reduction in semisolid medium, was supported by several carbon sources including malate and glucose. The N2 fixation activity was decreased if the oxygen concentration of the gas phase was lowered to one-tenth of atmospheric concentration. The highest specific nitrogenase activity recorded was 954 nmol C2H4/mg bacterial protein per hour, which is about 30% of that noted for Azospirillum lipoferum used as reference.

Acetylene↗
PubMed1999

Understanding plant-soil relationships using controlled environment facilities.

Although soil is a component of terrestrial ecosystems, it is comprised of a complex web of interacting organisms, and therefore can be considered itself as an ecosystem. Soil microflora and fauna derive energy from plants and plant residues and serve important functions in maintaining soil physical and chemical properties, thereby affecting net primary productivity (NPP), and in the case of contained environments, the quality of the life support system. We have been using 3 controlled-environment facilities (CEF's) that incorporate different levels of soil biological complexity and environmental control, and differ in their resemblance to natural ecosystems, to study relationships among plant physiology, soil ecology, fluxes of minerals and nutrients, and overall ecosystem function. The simplest system utilizes growth chambers and specialized root chambers with organic-less media to study the physiology of plant-mycorrhizal associations. A second system incorporates natural soil in open-top chambers to study soil bacterial and fungal population response to stress. The most complex CEF incorporates reconstructed soil profiles in a "constructed" ecosystem, enabling close examination of the soil foodweb. Our results show that closed ecosystem research is important for understanding mechanisms of response to ecosystem stresses. In addition, responses observed at one level of biological complexity may not allow prediction of response at a different level of biological complexity. In closed life support systems, incorporating soil foodwebs will require less artificial manipulation to maintain system stability and sustainability.

Biological Transport↗
PubMed1995

Salivary cortisol response to dental treatment of varying stress.

The physiologic stress of various dental procedures (dental examination, dental prophylaxis, restoration, root canal therapy, and tooth extraction) was measured in 50 nonsmoking healthy men between the ages of 18 and 55 years (mean 34.6 years, range 21 to 53 years) with a salivary cortisol assay. Expectorated saliva was collected at four time points: 10 minutes before the start of the procedure, 15 minutes after the patient was seated, at the end of the procedure, and 1 hour after the completion of the procedure. Of the 196 samples included for analysis, mean cortisol values ranged from 0.1 to 3.8 micrograms/dl with a recovery of 100% +/- 8.4%. The mean cortisol value for the extraction group (1.09 +/- 0.42 microgram/dl) was significantly different (p < 0.05) from the mean values of the examination (0.46 +/- 0.10 microgram/dl), prophylaxis (0.64 +/- 0.64 microgram/dl), root canal (0.49 +/- 0.07 microgram/dl), and restorative (0.60 +/- 0.04 microgram/dl) groups as determined by the Duncan's multiple range test. Cortisol levels decreased from the initial reading to the end of the procedure by about 15% for patients undergoing an examination, root canal, and restorative procedure. Cortisol levels at the end of the procedure were elevated in the prophylaxis (55%) and extraction (148%) groups compared with the baseline cortisol recording. A minority of patients in the prophylaxis group had elevated cortisol levels throughout dental treatment, whereas cortisol levels were elevated during treatment in 80% of patients undergoing extraction. These data suggest that the adrenal stress response associated with tooth extraction(s) is greater than that associated with other routine dental procedures.

Adolescent↗