Página 1 dos resultados de 376 itens digitais encontrados em 0.022 segundos

Mecanismos de patogenicidade do fungo Magnaporthe oryzae, agente causal da brusone em trigo: crescimento e esporulação, pressão de turgor apressorial, enzimas celulolíticas e produção de metabólitos tóxicos; Pathogenicity mechanisms of Magnaporthe oryzae, the causal agent of wheat blast: growth and sporulation, appressorial turgor pressure, cellulolytic activity and production of toxic metabolites

Melo, Thiago Anchieta de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/01/2014 PT
Relevância na Pesquisa
36.48%
O fungo Magnaporthe oryzae, agente causal da brusone em trigo e em várias outras gramíneas, desde o seu primeiro relato no Brasil tem sido alvo de inúmeras pesquisas. O entendimento da morfologia, fisiologia e parâmetros bioquímicos deste ascomiceto é o primeiro passo para a adoção de medidas eficientes de controle da doença. Os objetivos deste trabalho foram avaliar os aspectos morfológicos, fisiológicos e bioquímicos relativos à patogenicidade do fungo M. oryzae em trigo, além de determinar in vitro as condições ótimas de temperatura e fotoperíodo para o crescimento e esporulação dos isolados testados, quantificar a pressão de turgor exercida pelo apressório no momento da penetração do substrato, verificar a presença de enzimas extracelulares produzidas pelo patógeno e o papel de cada uma delas na degradação da parede celular e, também, demonstrar a possível produção e ação de metabólitos tóxicos do fungo em plântulas de trigo. Dois isolados do fungo, Py5003 e Py6017, foram repicados para os meios de cultivo cenoura, milho-cenoura, batata-dextrose-ágar (BDA), aveia e V8, incubados, de maneira independente, sob luz contínua, escuro contínuo e fotoperíodo de 12h, por 20 dias, sendo avaliados periodicamente quanto ao crescimento micelial total e esporulação do patógeno. Em seguida...

Influence of potassium and sodium nutrition on leaf area components in Eucalyptus grandis trees

Battie-Laclau, Patricia; Laclau, Jean-Paul; Piccolo, Marisa de Cassia; Arenque, Bruna Cersózimo; Beri, Constance; Mietton, Lauriane; Muniz, Marta R. Almeida; Jordan-Meille, Lionel; Buckeridge, Marcos Silveira; Nouvellon, Yann; Ranger, Jacques; Bouillet,
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 19-35
ENG
Relevância na Pesquisa
46.24%
Background and Aims: Recent studies showed a positive tree response to Na addition in K-depleted tropical soils. Our study aimed to gain insight into the effects of K and Na fertilizations on leaf area components for a widely planted tree species. Methods: Leaf expansion rates, as well as nutrient, polyol and soluble sugar concentrations, were measured from emergence to abscission of tagged leaves in 1-year-old Eucalyptus grandis plantations. Leaf cell size and water status parameters were compared 1 and 2 months after leaf emergence in plots with KCl application (+K), NaCl application (+Na) and control plots (C). Results: K and Na applications enhanced tree leaf area by increasing both leaf longevity and the mean area of individual leaves. Higher cell turgor in treatments +K and +Na than in the C treatment resulting from higher concentrations of osmotica contributed to increasing both palisade cell diameters and the size of fully expanded leaves. Conclusions: Intermediate total tree leaf area in treatment +Na compared to treatments C and +K might result from the capacity of Na to substitute K in osmoregulatory functions, whereas it seemed unable to accomplish other important K functions that contribute to delaying leaf senescence. © 2013 Springer Science+Business Media Dordrecht.

Turgor Regulation in Osmotically Stressed Arabidopsis Epidermal Root Cells. Direct Support for the Role of Inorganic Ion Uptake as Revealed by Concurrent Flux and Cell Turgor Measurements1

Shabala, Sergey N.; Lew, Roger R.
Fonte: American Society of Plant Physiologists Publicador: American Society of Plant Physiologists
Tipo: Artigo de Revista Científica
Publicado em /05/2002 EN
Relevância na Pesquisa
46.61%
Hyperosmotic stress is known to significantly enhance net uptake of inorganic ions into plant cells. Direct evidence for cell turgor recovery via such a mechanism, however, is still lacking. In the present study, we performed concurrent measurements of net ion fluxes (with the noninvasive microelectrode ion flux estimation technique) and cell turgor changes (with the pressure-probe technique) to provide direct evidence that inorganic ion uptake regulates turgor in osmotically stressed Arabidopsis epidermal root cells. Immediately after onset of hyperosmotic stress (100/100 mm mannitol/sorbitol treatment), the cell turgor dropped from 0.65 to about 0.25 MPa. Turgor recovery started within 2 to 10 min after the treatment and was accompanied by a significant (30–80 nmol m−2 s−1) increase in uptake of K+, Cl−, and Na+ by root cells. In most cells, almost complete (>90% of initial values) recovery of the cell turgor was observed within 40 to 50 min after stress onset. In another set of experiments, we combined the voltage-clamp and the microelectrode ion flux estimation techniques to show that this process is, in part, mediated by voltage-gated K+ transporters at the cell plasma membrane. The possible physiological significance of these findings is discussed.

The Biophysics of Leaf Growth in Salt-Stressed Barley. A Study at the Cell Level1

Fricke, Wieland; Peters, Winfried S.
Fonte: American Society of Plant Physiologists Publicador: American Society of Plant Physiologists
Tipo: Artigo de Revista Científica
Publicado em /05/2002 EN
Relevância na Pesquisa
36.46%
Biophysical parameters potentially involved in growth regulation were studied at the single-cell level in the third leaf of barley (Hordeum vulgare) after exposure to various degrees of NaCl stress for 3 to 5 d. Gradients of elongation growth were measured, and turgor pressure, osmolality, and water potentials (ψ) were determined (pressure probe and picoliter osmometry) in epidermal cells of the elongation zone and the mature blade. Cells in the elongation zone adjusted to decreasing external ψ through increases in cell osmolality that were accomplished by increased solute loads and reduced water contents. Cell turgor changed only slightly. In contrast, decreases in turgor also contributed significantly to ψ adjustment in the mature blade. Solute deposition rates in the elongation zone increased at moderate stress levels as compared with control conditions, but decreased again at more severe NaCl exposure. Growth-associated ψ gradients between expanding epidermal cells and the xylem were significant under control and moderate stress conditions (75 mm NaCl) but seemed negligible at severe stress (120 mm NaCl). We conclude that leaf cell elongation in NaCl-treated barley is probably limited by the rate at which solutes can be taken up to generate turgor...

Transient Responses of Cell Turgor and Growth of Maize Roots as Affected by Changes in Water Potential.

Frensch, J.; Hsiao, T. C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1994 EN
Relevância na Pesquisa
46.61%
Transient responses of cell turgor (P) and root elongation to changes in water potential were measured in maize (Zea mays L.) to evaluate mechanisms of adaptation to water stress. Changes of water potential were induced by exposing roots to solutions of KCl and mannitol (osmotic pressure about 0.3 MPa). Prior to a treatment, root elongation was about 1.2 mm h-1 and P was about 0.67 MPa across the cortex of the expansion zone (3-10 mm behind the root tip). Upon addition of an osmoticum, P decreased rapidly and growth stopped completely at pressure below approximately 0.6 MPa, which indicated that the yield threshold (Ytrans,1) was just below the initial turgor. Turgor recovered partly within the next 30 min and reached a new steady value at about 0.53 MPa. The root continued to elongate as soon as P rose above a new threshold (Ytrans,2) of about 0.45 MPa. The time between Ytrans,1 and Ytrans,2 was about 10 min. During this transition turgor gradients of as much as 0.15 MPa were measured across the cortex. They resulted from a faster rate of turgor recovery of cells deeper inside the tissue compared with cells near the root periphery. Presumably, the phloem was the source of the compounds for the osmotic adjustment. Turgor recovery was restricted to the expansion zone...

Physiological Control of Chloride Transport in Chara corallina1: I. EFFECTS OF LOW TEMPERATURE, CELL TURGOR PRESSURE, AND ANIONS

Sanders, Dale
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1981 EN
Relevância na Pesquisa
46.38%
The rate of Cl− transport at the plasma membrane of the freshwater alga Chara corallina is investigated with respect to possible in vivo controls acting in addition to the two well established ones of cytoplasmic Cl− and cytoplasmic pH. In contrast with results from many other plant tissues, halides appear to be the only anions capable of inhibiting Cl− transport, either from the outside or inside surfaces of the plasma membrane. Cell turgor pressure was also investigated. It was found that neither the influx of Cl− nor that of K+ or HCO2− is sensitive to turgor. Internal osmotic pressure is also insensitive to turgor, a situation contrasting with that in closely related brackish water charophytes.

Salinity Stress Inhibits Bean Leaf Expansion by Reducing Turgor, Not Wall Extensibility 1

Neumann, Peter M.; Van Volkenburgh, Elizabeth; Cleland, Robert E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1988 EN
Relevância na Pesquisa
36.44%
Treatment of bean (Phaseolus vulgaris L.) seedlings with low levels of salinity (50 or 100 millimolar NaCl) decreased the rate of light-induced leaf cell expansion in the primary leaves over a 3 day period. This decrease could be due to a reduction in one or both of the primary cellular growth parameters: wall extensibility and cell turgor. Wall extensibility was assessed by the Instron technique. Salinity did not decrease extensibility and caused small increases relative to the controls after 72 hours. On the other hand, 50 millimolar NaCl caused a significant reduction in leaf bulk turgor at 24 hours; adaptive decreases in leaf osmotic potential (osmotic adjustment) were more than compensated by parallel decreases in the xylem tension potential and the leaf apoplastic solute potential, resulting in a decreased leaf water potential. It is concluded that in bean seedlings, mild salinity initially affects leaf growth rate by a decrease in turgor rather than by a reduction in wall extensibility. Moreover, longterm salinization (10 days) resulted in an apparent mechanical adjustment, i.e. an increase in wall extensibility, which may help counteract reductions in turgor and maintain leaf growth rates.

Assimilate Unloading from Maize (Zea mays L.) Pedicel Tissues 1: I. Evidence for Regulation of Unloading by Cell Turgor

Porter, Gregory A.; Knievel, Daniel P.; Shannon, Jack C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1987 EN
Relevância na Pesquisa
46.44%
Sugar and 14C-assimilate release from the pedicel tissue of attached maize (Zea mays L.) kernels was studied following treatment with solute concentrations of up to 800 millimolal. Exposure and collection times ranged from 3 to 6 hours. Sugar and 14C-assimilate unloading and collection in agar traps was reduced by 25 and 43%, respectively, following exposure to 800 millimolal mannitol. Inhibition of unloading was not specific to mannitol, since similar concentrations of glucose, fructose, or equimolar glucose plus fructose resulted in comparable inhibition. Ethylene glycol, a rapidly permeating solute which should not greatly influence cell turgor, did not inhibit 14C-assimilate unloading. Based on these results, we suggest that inhibition of unloading by high concentrations of sugar or mannitol was due to reduced pedicel cell turgor. Changes in pedicel cell turgor may play a role in the regulation of assimilate transfer within the maize kernel.

Interaction of Cell Turgor and Hormones on Sucrose Uptake in Isolated Phloem of Celery 1

Daie, Jaleh
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1987 EN
Relevância na Pesquisa
46.65%
Phloem tissue isolated from celery (Apium graveolens L.) was used to investigate the regulation of sucrose uptake by turgor (manipulated by 50-400 milliosomolal solutions of polyethylene glycol) and hormones indoleacetic acid (IAA) and gibberillic acid (GA3). Sucrose uptake was enhanced under low cellular turgor (increase in the Vmax). Furthermore, enhancement of sucrose uptake was due to a net increase in influx rates since sucrose efflux was not affected by cell turgor. Manipulations of cell turgor had no effect on 3-O-methyl glucose uptake. When 20 millimolar buffer was present in uptake solutions, low turgor-induced effects were observed only at low pH range (4.5-5.5). However, the effect was extended to higher external pH (up to 7.5) when buffer was omitted from uptake solutions. A novel interaction between cellular turgor and hormone treatments was observed, in that GA3 (10 micromolar) and IAA (0.1-100 micromolar) enhanced sucrose uptake only at moderate turgor levels. The hormones elicited little or no response on sucrose uptake under conditions of low or high cell turgor. Low cell turgor, IAA, GA3, and fusicoccin caused acidification by isolated phloem segments in a buffer-free solution. It is suggested that enhanced sucrose uptake in response to low turgor and/or hormones was mediated through the plasmalemma H+-ATPase and most likely occurred at the site of loading.

Dynamic Relation between Expansion and Cellular Turgor in Growing Grape (Vitis vinifera L.) Leaves 1

Shackel, Kenneth A.; Matthews, Mark A.; Morrison, Janice C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1987 EN
Relevância na Pesquisa
36.6%
Measurements of the growth and water relations of expanding grape (Vitis vinifera L.) leaves have been used to determine the relationship between leaf expansion rate and leaf cell turgor. Direct measurement of turgor on the small (approximately 15 micrometer diameter) epidermal cells over the midvein of expanding grape leaves was made possible by improvements in the pressure probe technique. Leaf expansion rate and leaf water status were perturbed by environmentally induced changes in plant transpiration. After establishing a steady state growth rate, a step decrease in plant transpiration resulted in a rapid and large increase in leaf cell turgor (0.25 megapascal in 5 minutes), and leaf expansion rate. Subsequently, leaf expansion rate returned to the original steady state rate with no change in cell turgor. These results indicate that the expansion rate of leaves may not be strongly related to the turgor of the leaf cells, and that substantial control of leaf expansion rate, despite changes in turgor, may be part of normal plant function. It is suggested that a strictly physical interpretation of the parameters most commonly used to describe the relationship between turgor and growth in plant cells (cell wall extensibility and yield threshold) may be inappropriate when considering the process of plant cell expansion.

Sucrose Loading in Isolated Veins of Pisum sativum: Regulation by Abscisic Acid, Gibberellic Acid, and Cell Turgor 1

Estruch, Juan José; Peretó, Juli G.; Vercher, Yolanda; Beltrán, José Pío
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1989 EN
Relevância na Pesquisa
46.42%
Enzymatically isolated vein networks from mature pea (Pisum sativum L. cv Alaska) leaves were employed to investigate the properties of sucrose loading and the effect of phytohormones and cell turgor on this process. The sucrose uptake showed two components: a saturable and a first-order kinetics system. The high affinity system (Km, 3.3 millimolar) was located at the plasmalemma (p-chloromercuriphenylsulfonic acid and orthovanadate sensitivity). Further characterization of this system, including pH dependence and effects of energy metabolism inhibitors, supported the H+-sugar symport concept for sucrose loading. Within a physiological range (0.1-100 micromolar) and after 90 min, abscisic acid (ABA) inhibited and gibberellic acid (GA3) promoted 1 millimolar sucrose uptake. These responses were partially (ABA) or totally (GA3) turgor-dependent. In experiments of combined hormonal treatments, ABA counteracted the GA3 positive effects on sucrose uptake. The abolishment of these responses by p-chloromercuriphenylsulfonic acid and experiments on proton flux suggest that both factors (cell turgor and hormones) are modulating the H+ ATPase plasmalemma activity. The results are discussed in terms of their physiological relevance.

In Situ Measurement of Epidermal Cell Turgor, Leaf Water Potential, and Gas Exchange in Tradescantia virginiana L. 1

Shackel, Kenneth A.; Brinckmann, Enno
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1985 EN
Relevância na Pesquisa
46.49%
A combined system has been developed in which epidermal cell turgor, leaf water potential, and gas exchange were determined for transpiring leaves of Tradescantia virginiana L. Uniform and stable values of turgor were observed in epidermal cells (stomatal complex cells were not studied) under stable environmental conditions for both upper and lower epidermises. The changes in epidermal cell turgor that were associated with changes in leaf transpiration were larger than the changes in leaf water potential, indicating the presence of transpirationally induced within-leaf water potential gradients. Estimates of 3 to 5 millimoles per square meter per second per megapascal were obtained for the value of within-leaf hydraulic conductivity. Step changes in atmospheric humidity caused rapid changes in epidermal cell turgor with little or no initial change in stomatal conductance, indicating little direct relation between stomatal humidity response and epidermal water status. The significance of within-leaf water potential gradients to measurements of plant water potential and to current hypotheses regarding stomatal response to humidity is discussed.

Turgor Regulation of Sucrose Transport in Sugar Beet Taproot Tissue 1

Wyse, Roger E.; Zamski, Eliezer; Tomos, A. Deri
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1986 EN
Relevância na Pesquisa
36.67%
Sink tissues that store osmotically active compounds must osmoregulate to prevent excessively high turgor. The ability to regulate turgor may be related to membrane transport of solutes and thus sink strength. To study this possibility, the kinetics of sugar uptake were determined in sugar beet (Beta vulgaris L.) taproot tissue discs over a range of cell turgors. Sucrose uptake followed biphasic kinetics with a high affinity saturating component below 20 millimolar and a low affinity linear component at higher concentrations. Glucose uptake exhibited only simple saturation type kinetics. The high affinity saturating component of sucrose and glucose uptake was inhibited by increasing cell turgor (decreasing external mannitol concentrations). The inhibition was evident as a decrease in Vmax but no effect on Km. Sucrose uptake by tissue equilibrated in dilute buffer exhibited no saturating component. Ethylene glycol, a permeant osmoticum, had no effect on uptake kinetics, suggesting that the effect was due to changes in cell turgor and not due to decreased water potential per se. p-(Chloromercuri)benzene sulfonic acid (PCMBS) inhibited sucrose uptake at low but not high cell turgor. High cell turgor caused the tissue to become generally leaky to potassium...

Gradients of Turgor, Osmotic Pressure, and Water Potential in the Cortex of the Hypocotyl of Growing Ricinus Seedlings 1: Effects of the Supply of Water from the Xylem and of Solutes from the Phloem

Meshcheryakov, Anatoli; Steudle, Ernst; Komor, Ewald
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1992 EN
Relevância na Pesquisa
36.62%
To evaluate the possible role of solute transport during extension growth, water and solute relations of cortex cells of the growing hypocotyl of 5-day-old castor bean seedlings (Ricinus communis L.) were determined using the cell pressure probe. Because the osmotic pressure of individual cells (πi) was also determined, the water potential (ψ) could be evaluated as well at the cell level. In the rapidly growing part of the hypocotyl of well-watered plants, turgor increased from 0.37 megapascal in the outer to 1.04 megapascal in the inner cortex. Thus, there were steep gradients of turgor of up to 0.7 megapascal (7 bar) over a distance of only 470 micrometer. In the more basal and rather mature region, gradients were less pronounced. Because cell turgor ≈ πi and ψ ≈ 0 across the cortex, there were also no gradients of ψ across the tissue. Gradients of cell turgor and πi increased when the endosperm was removed from the cotyledons, allowing for a better water supply. They were reduced by increasing the osmotic pressure of the root medium or by cutting off the cotyledons or the entire hook. If the root was excised to interrupt the main source for water, effects became more pronounced. Gradients completely disappeared and turgor fell to 0.3 megapascal in all layers within 1.5 hours. When excised hypocotyls were infiltrated with 0.5 millimolar CaCl2 solution under pressure via the cut surface...

Quantitative Analysis of Photosynthate Unloading in Developing Seeds of Phaseolus vulgaris L. 1: II. Pathway and Turgor Sensitivity

Ellis, Erle C.; Turgeon, Robert; Spanswick, Roger M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1992 EN
Relevância na Pesquisa
36.51%
Phloem import and unloading in perfused bean (Phaseolus vulgaris L.) seed coats were investigated using steady-state labeling. Though photosynthate import and unloading were significantly reduced by perfusion, measurements of photosynthate fluxes in perfused seed coats proved useful for the study of unloading mechanisms in vivo. Phloem import was stimulated by lowered seed coat cell turgor, as demonstrated by an increase in tracer and sucrose import to seed coats perfused with high concentrations of an osmoticum. The partitioning of photosynthates between retention in the seed coat and release to the perfusion solution also was turgor sensitive; increases in seed coat cell turgor stimulated photosynthate release to the apoplast at the expense of photosynthate retention within the seed coat. There was no evidence of a turgor-sensitive sucrose uptake mechanism in perfused seed coats. Thus, the turgor sensitivity of photosynthate partitioning within perfused seed coats was consistent with a turgor-sensitive efflux control mechanism. Measurements of tracer equilibration and sugar partitioning in perfused seed coats provided strong evidence for symplastic phloem unloading in seed coats.

Cell Turgor Changes Associated with Ripening in Tomato Pericarp Tissue

Shackel, Kenneth A.; Greve, Carl; Labavitch, John M.; Ahmadi, Hamid
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1991 EN
Relevância na Pesquisa
36.53%
The pressure microprobe was used to determine whether the turgor pressure in tomato (Lycopersicon esculentum Mill., variety “Castelmart”) pericarp cells changed during fruit ripening. The turgor pressure of cells located 200 to 500 micrometers below the fruit epidermis was uniform within the same tissue (typically ± 0.02 megapascals), and the highest turgors observed (<0.2 megapascals) were much less than expected, based on tissue osmotic potential (−0.6 to −0.7 megapascals). These low turgor values may indicate the presence of apoplastic solutes. In both intact fruit and cultured discs of pericarp tissue, a small increase in turgor preceded the onset of ripening, and a decrease in turgor occurred during ripening. Differences in the turgor of individual intact fruit occurred 2 to 4 days before parallel differences in their ripening behavior were apparent, indicating that changes in turgor may reflect physiological changes at the cell level that precede expression of ripening at the tissue level.

Seasonal pattern of apoplastic solute accumulation and loss of cell turgor during ripening of Vitis vinifera fruit under field conditions

Wada, Hiroshi; Matthews, Mark A.; Shackel, Ken A.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em /04/2009 EN
Relevância na Pesquisa
46.23%
Using a novel pressure membrane (PM) apparatus for the extraction of apoplastic fluid from field-grown grape (Vitis vinifera L.) berries, our hypothesis that significant apoplast solutes accumulate at the beginning of the ripening process (i.e. veraison), and that this accumulation might contribute to progressive berry softening due to a progressive loss of mesocarp cell turgor pressure (P) was tested. It was necessary to correct the solute potential (Ψs) of fluid collected with the PM for dilution due to the presence of a dead volume in the apparatus, but after correction, the Ψs obtained with the PM agreed with that obtained by low speed centrifugation. A clear decline in fruit apoplastic solute potential (ψSA) began approximately 10 d prior to fruit coloration, and it was found to be coincident with a decline in mesocarp cell P and fruit elasticity (E). By late in fruit development when berry growth ceased (90 d after anthesis), both apoplast and fruit Ψs reached almost –4 MPa. These results support the hypothesis that a decrease in ψSA is responsible for the observed loss in mesocarp cell P, and is the mechanistic cause of berry softening.

Aquaporin-Mediated Reduction in Maize Root Hydraulic Conductivity Impacts Cell Turgor and Leaf Elongation Even without Changing Transpiration1[W]

Ehlert, Christina; Maurel, Christophe; Tardieu, François; Simonneau, Thierry
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /06/2009 EN
Relevância na Pesquisa
46.34%
Root hydraulic conductivity in plants (Lpr) exhibits large variations in response to abiotic stimuli. In this study, we investigated the impact of dynamic, aquaporin-mediated changes of Lpr on leaf growth, water potential, and water flux throughout the plant. For this, we manipulated Lpr by subjecting roots to four independent treatments, with aquaporin inhibitors applied either to transpiring maize (Zea mays) plants grown in hydroponics or to detopped root systems for estimation of Lpr. The treatments were acid load at pH 6.0 and 5.0 and hydrogen peroxide and anoxia applied for 1 to 2 h and subsequently reversed. First, we established that acid load affected cell hydraulic conductivity in maize root cortex. Lpr was reduced by all treatments by 31% to 63%, with half-times of about 15 min, and partly recovered when treatments were reversed. Cell turgor measured in the elongating zone of leaves decreased synchronously with Lpr, and leaf elongation rate closely followed these changes across all treatments in a dose-dependent manner. Leaf and xylem water potentials also followed changes in Lpr. Stomatal conductance and rates of transpiration and water uptake were not affected by Lpr reduction under low evaporative demand. Increased evaporative demand...

Loss of Stability: A New Look at the Physics of Cell Wall Behavior during Plant Cell Growth[W][OA]

Wei, Chunfang; Lintilhac, Philip M.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /11/2007 EN
Relevância na Pesquisa
36.6%
In this article we investigate aspects of turgor-driven plant cell growth within the framework of a model derived from the Eulerian concept of instability. In particular we explore the relationship between cell geometry and cell turgor pressure by extending loss of stability theory to encompass cylindrical cells. Beginning with an analysis of the three-dimensional stress and strain of a cylindrical pressure vessel, we demonstrate that loss of stability is the inevitable result of gradually increasing internal pressure in a cylindrical cell. The turgor pressure predictions based on this model differ from the more traditional viscoelastic or creep-based models in that they incorporate both cell geometry and wall mechanical properties in a single term. To confirm our predicted working turgor pressures, we obtained wall dimensions, elastic moduli, and turgor pressures of sequential internodal cells of intact Chara corallina plants by direct measurement. The results show that turgor pressure predictions based on loss of stability theory fall within the expected physiological range of turgor pressures for this plant. We also studied the effect of varying wall Poisson's ratio ν on extension growth in living cells, showing that while increasing elastic modulus has an understandably negative effect on wall expansion...

An Insight into Cell Elasticity and Load-Bearing Ability. Measurement and Theory

Wei, Chunfang; Lintilhac, Philip M.; Tanguay, Jason J.
Fonte: American Society of Plant Physiologists Publicador: American Society of Plant Physiologists
Tipo: Artigo de Revista Científica
Publicado em /07/2001 EN
Relevância na Pesquisa
36.54%
We have studied the elasticity and load bearing ability of plant tissue at the cellular level, using onion (Allium cepa) epidermal cells. The Young's modulus and Poisson's ratio of the cells were obtained by loading a tensile force on onion epidermal peels of different turgor pressures, and measuring the elongation and the lateral contraction of the peels. The Young's moduli and the Poisson's ratios ranged from 3.5 to 8.0 MPa and 0.18 to 0.30, respectively. To determine the effects of cell elasticity and turgor pressure on the cell's ability to bear load, we loaded a small glass ball onto a cell and measured the projected contact area between the ball and the cell. Unlike previous studies, we considered the cell as a whole entity, and utilized the Boussinesq's solution to derive the relevant equations that related the elastic parameters and cell deformation. For cells with a turgor pressure ≥ 0.34 MPa, the predicted contact area agreed well with the measured area. The equations could also predict cell turgor pressure with a deviation from the measured value of 0.01 MPa. This study gives strong support to ball tonometry, a new method of measuring cell turgor pressure.