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PubMed2003

Functional aspects of root architecture and mycorrhizal inoculation with respect to nutrient uptake capacity.

The aim of this research was to investigate the effect of arbuscular mycorrhizal (AM) colonisation on root morphology and nitrogen uptake capacity of carob (Ceratonia siliquaL.) under high and low nutrient conditions. The experimental design was a factorial arrangement of presence/absence of mycorrhizal fungus inoculation (Glomus intraradices) and high/low nutrient status. Percent AM colonisation, nitrate and ammonium uptake capacity, and nitrogen and phosphorus contents were determined in 3-month-old seedlings. Grayscale and colour images were used to study root morphology and topology, and to assess the relation between root pigmentation and physiological activities. AM colonisation lead to a higher allocation of biomass to white and yellow parts of the root. Inorganic nitrogen uptake capacity per unit root length and nitrogen content were greatest in AM colonised plants grown under low nutrient conditions. A better match was found between plant nitrogen content and biomass accumulation, than between plant phosphorus content and biomass accumulation. It is suggested that the increase in nutrient uptake capacity of AM colonised roots is dependent both on changes in root morphology and physiological uptake potential. This study contributes to an understanding of the role of AM fungi and root morphology in plant nutrient uptake and shows that AM colonisation improves the nitrogen nutrition of plants, mainly when growing at low levels of nutrients.

Fabaceae↗

PubMed2006

Callose in root apices of European chestnut seedlings: a physiological indicator of aluminum stress.

We determined if callose formation in 1-cm-long root apices of European chestnut (Castanea sativa Mill.) seedlings is affected by naturally occurring high concentrations of aluminum (Al) under laboratory conditions and by low base saturation (BS) of soils under forest field conditions. Under controlled conditions in the laboratory, seedlings were treated with simulated soil solutions in the presence or absence (control) of Al. One day after exposing seedlings to a simulated soil solution containing 168 microM Al, callose formation in the root apices had increased significantly. After 7 days, callose concentration in root apices was significantly correlated with the concentration of free Al3+ ions recovered in the simulated soil solution and with the concentration of Al in fine roots. At four field sites in southern Switzerland, seedlings were grown for five months in either A-horizon soil with a BS above 17% or in a B-horizon soil with a BS below 5%. Callose concentrations were significantly higher in root apices in the B horizon than in the A horizon. Callose concentrations in root apices were negatively correlated with Ca/Al molar ratio in fine roots. We conclude that callose in the root apices of European chestnut could be a useful physiological parameter for assessing Al toxicity under both laboratory and field conditions.

Aluminum↗

PubMed1985

Flexion reflex elicited by ventral root afferents in the cat.

To investigate the physiological role of ventral root afferent fibers, the ventral root was stimulated in spinal cats in an attempt to elicit the flexion reflex, a common nociceptive spinal reflex. The flexion reflex was elicited by stimulating the distal stump of the cut L7 or S1 ventral root and recorded from the proximal stump of the cut S1 ventral root. In 12 of the 14 cats studied, the flexion reflex was recorded as a compound action potential. The finding was confirmed by recording single-unit activity from 5 units in two cats. These results suggest that the ventral root afferent fibers exert a variety of physiological effects that include eliciting such spinal reflexes as the flexion reflex. The responsible fibers in the ventral root travel distally towards the dorsal root ganglion to enter the spinal cord through the dorsal root.

Action Potentials↗

PubMed1977

Physiological and biochemical studies on senescing tap root nodules of soybeans.

Senescence of soybean (Glycine max L. Merr.) tap root nodules was investigated by comparing changes in various physiological and biochemical activities with changes in capacity to fix nitrogen. Field-grown Beeson and Calland varieties of soybeans of various ages were sources of tap root nodules. With both varieties, the number of tap root nodules per plant remained constant between 56 and 86 days after planting but fresh weight, dry weight, and mass of tap root nodules increased duing this period. Nitrogen (C2H2)fixation by attached tap root nodules was maximum on a fresh weight, dry weight, or nitrogen basis about 56 days after planting for either variety. Metabolic activities of bacteroids as measured by carbon dioxide evolution from glucose and succinate did not appear to vary among nodules of different ages. There was also no indication of mobilization or deposition or deposition of iron, molybdenum, calcium, zinc, and nitrate in aging tap root nodules. Nitrate levels in the aerial portion of the plants decreased significantly after the initial decline in acetylene reduction. Nicotinamide deamidase activity in the cytosol and in extracts of bacteroids did not change significantly as tap root nodules aged. However, significant and consistent changes were observed in initial pH values of nodule breis and the initial decline occurred before (Calland) or concurrently (Beeson) with the initial decline of nitrogen fixation.

Bacteria↗

PubMedDate not supplied

[Patterns of cell functioning in starvation (exemplified by isolated roots)].

Comparison is made over physiology of the cells of isolated roots with those of animals under long-term starvation conditions. General mechanisms of functioning of such cells are exposed. It is shown that cut-off roots could be used as proper model for the studying physiology of the cell starvation.

Animals↗

PubMed2001

Isolation and characterisation of a cassava catalase expressed during post-harvest physiological deterioration.

Storage roots of cassava undergo a rapid, endogenous, post-harvest deterioration response that is thought to involve oxidative processes. A cassava catalase (MecCAT1) was isolated from a root cDNA library. The transcript is expressed predominantly in roots with little expression in leaves. Catalase enzyme activity and MecCAT1 transcript expression during the post-harvest period were compared in highly susceptible and less susceptible cultivars and suggest that high levels of catalase activity may play a role in delaying the deterioration response.

Amino Acid Sequence↗

PubMed1969

Ethylene and carbon dioxide in the growth and development of cultured radish roots.

Ethylene is produced by cultured radish roots in amounts large enough to be physiologically important. When roots were grown in controlled atmospheres, applied ethylene was generally inhibitory to elongation, lateral root initiation, and cambial activity. 1% CO(2) similarly affected roots not given ethylene. In contrast, elongation and lateral root production of ethylene-treated roots were stimulated by 1% CO(2). The results suggest that the often-observed stimulation of root growth by CO(2) is due to an interaction with endogenous ethylene.

Journal Article↗

PubMed2006

Specialized 'dauciform' roots of Cyperaceae are structurally distinct, but functionally analogous with 'cluster' roots.

When grown in nutrient solutions of extremely low [P] (<or=1.0 microm), the sedge Schoenus unispiculatus Benth. (Cyperaceae) develops dauciform roots, which are short and carrot shaped, and produce dense numbers of long root hairs. It has been suggested that dauciform roots of monocotyledonous sedges function to acquire P from nutrient-poor, P-fixing soils in a manner similar to that of cluster (proteoid) roots developed by some dicotyledonous species, but without evidence to substantiate this claim. To elucidate the ecophysiological role of dauciform roots, we assessed carboxylate exudation, internal carboxylate and P concentrations and O(2) uptake rates during dauciform root development. We showed that O(2) consumption was fastest [9 nmol O(2) g(-1) fresh mass (FM) s(-1)] and root [P] greatest (0.4 mg P g(-1) FM) when dauciform roots were young and rapidly developing. Citrate was the most abundant carboxylate in root tissues at all developmental stages, and was most concentrated (22.2 micromol citrate g(-1) FM) in young dauciform roots, decreasing by more than half in mature dauciform roots. Peak citrate-exudation rates (1.7 nmol citrate g(-1) FM s(-1)) occurred from mature dauciform roots, and were approximately an order of magnitude faster than those from roots of species without root clusters, and similar to those of mature proteoid (cluster) roots of Proteaceae. Both developing and mature dauciform roots had the capacity to acidify (but not alkalinize) the rhizosphere. Anatomical studies showed that epidermal cells in dauciform roots were greatly elongated in the transverse plane; epidermal cells of parent roots were unmodified. Although structurally distinct, the physiology of dauciform roots in sedges appears to be analogous to that of proteoid roots of Proteaceae and Fabaceae, and hence, dauciform roots would facilitate access to sorbed P and micronutrients from soils of low fertility.

Carboxylic Acids↗

PubMed2002

Physiologic bladder evacuation with selective sacral root stimulation: sinusoidal signal and organ-specific frequency.

In patients with spinal cord injury above S2, who characteristically have both detrusor hyperflexia and sphincteric spasm, sacral anterior root stimulation can evacuate the bladder, but sacral deafferentation is needed to eliminate the hyperreflexia for normal bladder filling. The common stimulation parameters for these patients activate the detrusor and the external urethral sphincter simultaneously (detrusor-sphincter dyssynergia), and the resultant post-stimulus voiding is not physiologic. We sought to determine organ-specific stimulation parameters. In 20 male dogs, the rectangular pulse and sinusoidal signal forms were evaluated with a variety of parameters for stimulation of S2 and S3 anterior roots extra- and intradurally (i.e., stimulation frequency and voltage, uni- versus bilateral electrode placement, and degree of bladder filling). New torpedo-shaped bipolar electrodes were used, adjusted to neural diameter. The best results were recorded with intradural bilateral sinusoidal signal. Sphincteric fatigue was produced by pre-stimulating S2 with 104+/-17 Hz and 0.8+/-0.1 V for 10 to 15 seconds before S3 stimulation. S3 stimulation with 16+/- 2.1 Hz and 0.4+/-0.1 V evoked a detrusor pressure of 28.7+/-3.0 cm H2O above the sphincteric pressure. Selective anterior root stimulation with organ-specific stimulation parameters can effect initial sphincteric fatigue to achieve physiologic voiding.

Animals↗

PubMed2004

[Response of fine roots to soil nutrient spatial heterogeneity].

The spatial heterogeneity is the complexity and variation of systems or their attributes, and the heterogeneity of soil nutrients is ubiquitous in all natural ecosystems. The scale of spatial heterogeneity varies considerably among different ecosystems, from tens of centimeters to hundred meters. Some of the scales can be detected by individual plant. Because the growth of individual plants can be strongly influenced by soil heterogeneity, it follows that the inter-specific competition should also be affected. During the long process of evolution, plants developed various plastic responses with their root system, including morphological, physiological and mycorrhizal plasticity, to maximize the nutrient acquisition from heterogeneous soil resources. Morphological plasticity, an adjustment in root system spatial allocation and architecture in response to spatial heterogeneous distribution of available soil resources, has been most intensively studied, and root proliferation in nutrient rich patches has been certified for many species. The species that do respond may have an increased rate of nutrient uptake, leading to a competitive advantage. Scale and precision are two important features employed in describing the size and foraging behavior of root system. It was hypothesized that scale and precision is negatively related, i. e., the species with high scale of root system tend to be a less precise forager. The outcomes of different research work have been diverse, far from reaching a consensus. Species with high scale are not necessarily less precise in fine root allocation, and vice versa. The proliferation of fine root in enriched micro-sites is species dependent, and also affected by other factors, such as patch attributes (size and nutrients concentration), nutrients, and overall soil fertility. Beside root proliferation in nutrient enriched patches, plants can also adapt themselves to the heterogeneous soil environment by altering other root characteristics such as fine root diameter, branch angle, length, and spatial architecture of root system. Physiological and mycorrhizal plasticity can add some influence on the morphological plasticity to some extent, but they are less studied. Roots located in different patches can quickly regulate their nutrient uptake kinetics within different nutrient patches, and increase overall nutrient uptake. Physiological response may, to certain extent, reduce morphological response, and is meaningful for plant growth on soils with frequently changing spatial and temporal heterogeneity. Mycorrhizal plasticity has been least studied so far. Some researches revealed that mycorrhiza, rather than fine root, proliferated in enriched patches. But, it is not the case with other studies. The proliferation of mycorrhiza within enriched patches is more profitable in term of carbon invest. The effect of fine root proliferation on nutrient uptake is complex, depending on ion mobility and whether or not neighboring plant exists. The influence of root plasticity on the growth of plants is species specific. Some species (sensitive species) gain growth benefit, while others don't. The ability of an individual plant to response to heterogeneous resources has significant effect on its competitive ability and its fate within the community, and eventually shapes the composition and structure of the community.

Adaptation, Physiological↗

PubMed2000

Signal detection theory in the 2AFC paradigm: attention, channel uncertainty and probability summation.

Neural implementation of classical High-Threshold Theory reveals fundamental flaws in its applicability to realistic neural systems and to the two-alternative forced-choice (2AFC) paradigm. For 2AFC, Signal Detection Theory provides a basis for accurate analysis of the observer's attentional strategy and effective degree of probability summation over attended neural channels. The resulting theory provides substantially different predictions from those of previous approximation analyses. In additive noise, attentional probability summation depends on the attentional model assumed. (1) For an ideal attentional strategy in additive noise, summation proceeds at a diminishing rate from an initial level of fourth-root summation for the first few channels. The maximum improvement asymptotes to about a factor of 4 by a million channels. (2) For a fixed attention field in additive noise, detection is highly inefficient at first and approximates fourth-root summation through the summation range. (3) In physiologically plausible root-multiplicative noise, on the other hand, attentional probability summation mimics a linear improvement in sensitivity up to about ten channels, approaching a factor of 1000 by a million channels. (4) Some noise sources, such as noise from eye movements, are fully multiplicative and would prevent threshold determination within their range of effectiveness. Such results may require reappraisal of previous interpretations of detection behavior in the 2AFC paradigm.

Attention↗

PubMed1996

The effects of asymmetric calcium application on primary root curvature of ageotropum pea mutant.

Recent studies indicate that roots of ageotropum seedlings can be used to study the hydrotropic response of roots independent of physiological events related to the gravity response of roots. There is evidence that Ca2+ ions are important in both the gravitropic and hydrotropic response of roots. In this study, we have compared three fully graviresponsive pea cultivars and the ageotropum mutant with regard to: 1) general root anatomy, 2) the effects of unilateral Ca application to both the root cap and DEZ region on root curvature, and 4) effects of unilateral application of EGTA to the DEZ region.

Calcium↗

PubMed1988

Drought tolerance, growth partitioning and vigor in eucalypt seedlings and rooted cuttings.

To clarify the physiological basis of productivity differences among rooted cuttings and seedlings of eucalypt species, relationships between morphology and water relations were examined in 4-month-old seedlings of Eucalyptus grandis W. Hill ex Maiden, E. urophylla S.T. Blake and E. cloeziana F. Muell. and in 4-month-old rooted cuttings of three E. grandis cultivars. Four-month-old seedlings had greater dry weights, lower leaf area/root dry weight (LA/RDW) ratios and lower shoot/root dry weight (S/R) ratios than 4-month-old rooted cuttings. For all cultivars of E. grandis, tall rooted cuttings, as defined by height at age 4 weeks, had greater dry weights by age 4 months and lower LA/RDW and S/R ratios than short rooted cuttings. There were differences in height growth, dry matter productivity and relative shoot and root development among cuttings of different E. grandis cultivars, but these differences were not as great as the differences between short and tall grades of the same cultivar and between seedlings and cuttings. Consistent with the differences in LA/RDW and S/R ratios, seedlings had higher daytime water potentials (Psi(x)) than cuttings, and tall cuttings had higher daytime values of Psi(x) than short cuttings. Differences in Psi(x) were also related to stomatal conductance (g(wv)), which was up to 300% greater in short cuttings than in tall cuttings. Among seedlings, those of E. cloeziana, which had the smallest dry weight at age 4 months, had the highest g(wv), whereas those of E. grandis, which had the greatest dry weight at age 4 months, had the lowest g(wv). Unlike seedlings and the tall cuttings, short cuttings lost turgor when subjected to drought. The differences observed in susceptibility to water stress may account in part for the associated differences in dry matter production. Xylem pressure potential and relative water deficit at zero turgor did not differ significantly among the types of plants studied, which suggests that differences in growth rates were not the result of differences in dehydration tolerance.

Journal Article↗

PubMed2006

Predictable root recession coverage.

Gingival recession, exposure of the tooth's root, is undesirable and, in many situations, contrary to normal physiology. Today's root coverage is predictable. With the use of an acellular dermal matrix membrane (Fasciablast), we can achieve a new blood supply and predictable coverage, with no second surgical procedure. Youth, esthetics and physiology are restored.

Biocompatible Materials↗

PubMed1998

Root growth and oxygen relations at low water potentials. Impact Of oxygen availability in polyethylene glycol solutions

Polyethylene glycol (PEG), which is often used to impose low water potentials (psiw) in solution culture, decreases O2 movement by increasing solution viscosity. We investigated whether this property causes O2 deficiency that affects the elongation or metabolism of maize (Zea mays L.) primary roots. Seedlings grown in vigorously aerated PEG solutions at ambient solution O2 partial pressure (pO2) had decreased steady-state root elongation rates, increased root-tip alanine concentrations, and decreased root-tip proline concentrations relative to seedlings grown in PEG solutions of above-ambient pO2 (alanine and proline accumulation are responses to hypoxia and low psiw, respectively). Measurements of root pO2 were made using an O2 microsensor to ensure that increased solution pO2 did not increase root pO2 above physiological levels. In oxygenated PEG solutions that gave maximal root elongation rates, root pO2 was similar to or less than (depending on depth in the tissue) pO2 of roots growing in vermiculite at the same psiw. Even without PEG, high solution pO2 was necessary to raise root pO2 to the levels found in vermiculite-grown roots. Vermiculite was used for comparison because it has large air spaces that allow free movement of O2 to the root surface. The results show that supplemental oxygenation is required to avoid hypoxia in PEG solutions. Also, the data suggest that the O2 demand of the root elongation zone may be greater at low relative to high psiw, compounding the effect of PEG on O2 supply. Under O2-sufficient conditions root elongation was substantially less sensitive to the low psiw imposed by PEG than that imposed by dry vermiculite.

Journal Article↗

PubMed1990

Fe uptake mechanism in fe-efficient cucumber roots.

Fe-efficient plants respond to iron stress both by morphological and physiological modifications. In roots of a Fe-efficient plant (Cucumis sativus L.) grown in the presence or in the absence of iron, the capacity to acidify the external medium, change in the transmembrane electrical potential, and the ATPase activity have been determined. Roots from plants grown in the absence of iron showed a great capacity to acidify the external medium, a higher transmembrane electrical potential difference (-145 millivolts, versus -105 millivolts), and a higher ATPase activity (+30%). The administration of Fe(2+), but not Fe(3+), caused a block of the acidification capacity, a great decrease in the transmembrane electrical potential difference in root cells, and a large inhibition of the ATPase activity of isolated microsomal membrane vesicles.

Journal Article↗

PubMed1994

Mitochondria buffer physiological calcium loads in cultured rat dorsal root ganglion neurons.

We sought to determine whether low-affinity, high-capacity mitochondrial Ca2+ uptake contributes to buffering physiological Ca2+ loads in sensory neurons. Intracellular free calcium concentration ([Ca2+]i) and intracellular free hydrogen ion concentration ([H+]i) were measured in single rat dorsal root ganglion (DRG) neurons grown in primary culture using indo-1 and carboxy-SNARF-based dual emission microfluorimetry. Field potential stimulation evoked action potential-mediated increases in [Ca2+]. Brief trains of action potentials elicited [Ca2+]i transients that recovered to basal levels by a single exponential process. Trains of > 25 action potentials elicited larger increases in [Ca2+]i, recovery from which consisted of three distinct phases. During a rapid initial phase [Ca2+]i decreased to a plateau level (450-550 nM). The plateau was followed by a slow return to basal [Ca2+]i [Ca2+]i transients elicited by 40-50 action potentials in the presence of the mitochondrial uncoupler carbonyl cyanide chlorophenyl hydrazone (CCCP), or the electron transport inhibitor antimycin A1, lacked the plateau, and the recovery to basal [Ca2+]i consisted of a single slow phase. Depolarization with 50 mM K+ produced a multiphasic [Ca2+]i transient and increased [H+]i from 74 +/- 3 to 107 +/- 8 nM. The rise in [H+]i was dependent upon extracellular Ca2+ and was inhibited by mitochondrial poisons. With mitochondrial Ca2+ buffering pharmacologically blocked, the recovery to basal [Ca2+]i was unaffected by removal of extracellular Na+. We conclude that large Ca2+ loads are initially buffered by fast mitochondrial sequestration that effectively uncouples electron transport from ATP synthesis, leading to an increase in [H+]i. Small Ca2+ loads are buffered by a nonmitochondrial, Na(+)-independent process.

Action Potentials↗

PubMed1999

[Dorsal root identification using spinal endoscopy and electro-physiology].

We aimed to develop a method of accurately identifying the dorsal root for the corresponding peripheral afferent nerve under endoscopic observation. We developed an endoscope with an external diameter of 1.8 mm. After small laminectomy on the lower thoracic vertebrae, we inserted this endoscope carefully into the epidural and then subarachnoid spaces. We observed structures in these spaces with the endoscope. We tried to determine the spatial relationship between these electrodes and dorsal root. After identifying each space, we inserted two electrodes into the visualized space to record evoked potentials; a bipolar electrode (protocol 1) and a catheter-type eight polar electrode (protocol 2). Each pole could be distinguished by marks. To stimulate peripheral nerves, we inserted needle-type electrodes into Th 10, 11 and 12 intercostal nerves. We attempted to record potentials from dorsal surface of the cord generated by intercostal nerve stimulus. Protocol 1: We moved the position of the bipolar recording electrodes between Th 9 and L 1 by 1 cm increment, and obtained evoked potentials correspondingly. Protocol 2: We chose the neighboring pairs of poles sequentially from the tip of the catheter for bipolar recording. At the end of each experiment, we dissected the animal and checked the intercostal nerve originating from the root. With the endoscope, we could clearly observe structures in the epidural and subarachnoid spaces. We could record evoked potentials from the dorsal spinal cord with the electrodes located either in epidural or in subarachnoid spaces. Shapes of evoked potentials changed characteristically according to the relative position between the root and the electrode. The largest potentials were obtained when the electrode was nearest to the dorsal root, of which the peripheral nerve was being stimulated. By combining endoscopy with the electrophysiological technique, we could accurately identify the dorsal roots for the corresponding peripheral afferent nerves. This method may be used for the selective dorsal root blockade under the visual field.

Animals↗