Home About us Contact
|
Home About us Contact | ||
|
|
||
Turgor Pressure (turgor + pressure)
Selected AbstractsIntercellular adhesion and cell separation in plantsPLANT CELL & ENVIRONMENT, Issue 7 2003M. C. JARVIS ABSTRACT Adhesion between plant cells is a fundamental feature of plant growth and development, and an essential part of the strategy by which growing plants achieve mechanical strength. Turgor pressure provides non-woody plant tissues with mechanical rigidity and the driving force for growth, but at the same time it generates large forces tending to separate cells. These are resisted by reinforcing zones located precisely at the points of maximum stress. In dicots the reinforcing zones are occupied by networks of specific pectic polymers. The mechanisms by which these networks cohere vary and are not fully understood. In the Poaceae their place is taken by phenolic cross-linking of arabinoxylans. Whatever the reinforcing polymers, a targeting mechanism is necessary to ensure that they become immobilized at the appropriate location, and there are secretory mutants that appear to have defects in this mechanism and hence are defective in cell adhesion. At the outer surface of most plant parts, the tendency of cells to cohere is blocked, apparently by the cuticle. Mutants with lesions in the biosynthesis of cuticular lipids show aberrant surface adhesion and other developmental abnormalities. When plant cells separate, the polymer networks that join them are locally dismantled with surgical precision. This occurs during the development of intercellular spaces; during the abscission of leaves and floral organs; during the release of seeds and pollen; during differentiation of root cap cells; and during fruit ripening. Each of these cell separation processes has its own distinctive features. Cell separation can also be induced during cooking or processing of fruit and vegetables, and the degree to which it occurs is a significant quality characteristic in potatoes, pulses, tomatoes, apples and other fruit. Control over these technological characteristics will be facilitated by understanding the role of cell adhesion and separation in the life of plants. [source] Turgor pressure, membrane tension and the control of exocytosis in higher plantsPLANT CELL & ENVIRONMENT, Issue 9 2000Wieland Fricke ABSTRACT Both turgor pressure and differences in membrane tension are capable of providing an energy input into exocytosis, the process of fusion of Golgi vesicles with the cell membrane in plants. It is shown that the contribution of turgor pressure is much larger than that of membrane tension, so that the exocytotic process is not likely on thermodynamic grounds to be reversible unless another source of energy is made available. However, recycling of membrane material as flattened, empty vesicles is energetically possible and is likely to be favoured when the magnitude of membrane tension in the cell membrane is low. Thus the outward flows of membrane and cell wall material are in principle linked to turgor, whereas membrane tension influences the inward flow of membrane material. [source] Gastrulation in the sea urchin embryo: A model system for analyzing the morphogenesis of a monolayered epitheliumDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 4 2004Tetsuya Kominami Processes of gastrulation in the sea urchin embryo have been intensively studied to reveal the mechanisms involved in the invagination of a monolayered epithelium. It is widely accepted that the invagination proceeds in two steps (primary and secondary invagination) until the archenteron reaches the apical plate, and that the constituent cells of the resulting archenteron are exclusively derived from the veg2 tier of blastomeres formed at the 60-cell stage. However, recent studies have shown that the recruitment of the archenteron cells lasts as late as the late prism stage, and some descendants of veg1 blastomeres are also recruited into the archenteron. In this review, we first illustrate the current outline of sea urchin gastrulation. Second, several factors, such as cytoskeletons, cell contact and extracellular matrix, will be discussed in relation to the cellular and mechanical basis of gastrulation. Third, differences in the manner of gastrulation among sea urchin species will be described; in some species, the archenteron does not elongate stepwise but continuously. In those embryos, bottle cells are scarcely observed, and the archenteron cells are not rearranged during invagination unlike in typical sea urchins. Attention will be also paid to some other factors, such as the turgor pressure of blastocoele and the force generated by blastocoele wall. These factors, in spite of their significance, have been neglected in the analysis of sea urchin gastrulation. Lastly, we will discuss how behavior of pigment cells defines the manner of gastrulation, because pigment cells recently turned out to be the bottle cells that trigger the initial inward bending of the vegetal plate. [source] Osmoadaptation in bacteria and archaea: common principles and differencesENVIRONMENTAL MICROBIOLOGY, Issue 12 2001Markus Roeßler The availability of water is the most important prerequisite for life of any living cell, and exposure of cells to hypersaline conditions always threatens the cells with a drastic loss of water. To re-establish the essential turgor pressure, cells increase the water activity of their cytoplasm by accumulation of compatible solutes, either by synthesis or by uptake. The ability to respond to increasing osmolality is well conserved in all three lines of descent and, here, we compare the osmoadaptive strategies of Bacteria and Archaea. The temporal sequence of events after an osmotic upshock will be discussed, with a focus on the most rapid response, notably the mechanisms of transport activation at the protein level, and different signals for osmolality will be compared. The spectrum of compatible solutes used by different organisms is rather diverse and a comparison of ,bacterial' and ,archaeal' compatible solutes will be given. [source] Fungal cannons: explosive spore discharge in the AscomycotaFEMS MICROBIOLOGY LETTERS, Issue 1 2007Frances Trail Abstract The ascomycetous fungi produce prodigious amounts of spores through both asexual and sexual reproduction. Their sexual spores (ascospores) develop within tubular sacs called asci that act as small water cannons and expel the spores into the air. Dispersal of spores by forcible discharge is important for dissemination of many fungal plant diseases and for the dispersal of many saprophytic fungi. The mechanism has long been thought to be driven by turgor pressure within the extending ascus; however, relatively little genetic and physiological work has been carried out on the mechanism. Recent studies have measured the pressures within the ascus and quantified the components of the ascus epiplasmic fluid that contribute to the osmotic potential. Few species have been examined in detail, but the results indicate diversity in ascus function that reflects ascus size, fruiting body type, and the niche of the particular species. [source] The release of elongated, sheathed ascospores from bottle-shaped asci in Dipodascus geniculatusFEMS YEAST RESEARCH, Issue 2 2007Ané Van Heerden Abstract Yeasts use different mechanisms to release ascospores of different lengths from bottle-shaped asci. Round to oval-shaped ascospores are enveloped in oxylipin-coated compressible sheaths, enabling ascospores to slide past each other when they reach the narrowing ascus neck. However, more elongated ascospores do not contain sheaths, but are linked by means of oxylipin-coated interlocked hooked ridges on the surfaces of neighboring ascospores, thereby keeping them aligned while they are pushed towards the ascus tip by turgor pressure. In this study, we found elongated, oxylipin-coated sheathed ascospores in Dipodascus geniculatus that are released effectively from bottle-shaped asci without alignment. This is possible because the ascus neck and opening have a diameter that is the same as the length of the ascospore, thus allowing the ascospores to turn sideways without blocking the ascus when they are released. We found that increased concentrations of acetylsalicylic acid inhibit both ascospore release and 3-hydroxy oxylipin production in this yeast, thereby implicating this oxylipin in sexual reproduction. [source] Exogenous Glycinebetaine and Salicylic Acid Application Improves Water Relations, Allometry and Quality of Hybrid Sunflower under Water Deficit ConditionsJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2009M. Hussain Abstract Limited water availability hampers the sustainability of crop production. Exogenous application of glycinebetaine (GB) and salicylic acid (SA) has been found very effective in reducing the adverse effects of water scarcity. This study was conducted to examine the possible role of exogenous GB and SA application in improving the growth and water relations of hybrid sunflower (Helianthus annuus L.) under different irrigation regimes. There were three levels of irrigation, viz. control (normal irrigations), water stress at budding stage (irrigation missing at budding stage) and water stress at flowering stage (FS) (irrigation missing at FS). GB and SA were applied exogenously at 100 and 0.724 mm respectively, each at the budding and FS. Control plants did not receive application of GB and SA. Water stress reduced the leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), leaf relative water contents, water potential, osmotic potential, turgor pressure, achene yield and water use efficiency. Nevertheless, exogenous GB and SA application appreciably improved these attributes under water stress. However, exogenous GB application at the FS was more effective than other treatments. Net assimilation rate was not affected by water stress as well as application of GB and SA. The protein contents were considerably increased by water stress at different growth stages, but were reduced by exogenous GB and SA application. The effects of water stress and foliar application of GB were more pronounced when applied at FS than at the budding stage. Moreover, exogenous GB application was only advantageous under stress conditions. [source] Contribution of Cellular Structure to the Large and Small Deformation Rheological Behavior of KiwifruitJOURNAL OF FOOD SCIENCE, Issue 6 2002A.M. Rojas ABSTRACT: The relative contribution of turgor pressure, cell wall and middle lamellae to the rheology of kiwifruit was studied by performing large deformation assays and using an empirical model proposed by our group. Results were compared with those obtained previously through dynamic testing. Initial (,0) and residual relaxation (,,) stresses determined under 14% constant deformation correlated significantly with complex moduli (G*) and they allowed to detect incipient plasmolysis but not to determine the individual contributions of cell wall and middle lamellae to tissue elasticity. Firmness (Fm) showed no correlation with G* because measurement of failure stress required tissue damage but it was affected by ripening allowing to determine the individual contributions of cell wall and middle lamellae to its value. [source] Mechanical Response of Single Plant Cells to Cell Poking: A Numerical Simulation ModelJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2006Rong Wang Abstract Cell poking is an experimental technique that is widely used to study the mechanical properties of plant cells. A full understanding of the mechanical responses of plant cells to poking force is helpful for experimental work. The aim of this study was to numerically investigate the stress distribution of the cell wall, cell turgor, and deformation of plant cells in response to applied poking force. Furthermore, the locations damaged during poking were analyzed. The model simulates cell poking, with the cell treated as a spherical, homogeneous, isotropic elastic membrane, filled with incompressible, highly viscous liquid. Equilibrium equations for the contact region and the non-contact regions were determined by using membrane theory. The boundary conditions and continuity conditions for the solution of the problem were found. The force-deformation curve, turgor pressure and tension of the cell wall under cell poking conditions were obtained. The tension of the cell wall circumference was larger than that of the meridian. In general, maximal stress occurred at the equator around. When cell deformation increased to a certain level, the tension at the poker tip exceeded that of the equator. Breakage of the cell wall may start from the equator or the poker tip, depending on the deformation. A nonlinear model is suitable for estimating turgor, stress, and stiffness, and numerical simulation is a powerful method for determining plant cell mechanical properties. (Managing editor: Wei Wang) [source] The linkage between cell wall metabolism and fruit softening: looking to the futureJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2007Ariel R Vicente Abstract The softening that accompanies ripening of commercially important fruits exacerbates damage incurred during shipping and handling and increases pathogen susceptibility. Thus, postharvest biologists have studied fruit softening to identify ways to manage ripening and optimise fruit quality. Studies, generally based on the premise that cell wall polysaccharide breakdown causes ripening-associated softening, have not provided the insights needed to genetically engineer, or selectively breed for, fruits whose softening can be adequately controlled. Herein it is argued that a more holistic view of fruit softening is required. Polysaccharide metabolism is undoubtedly important, but understanding this requires a full appreciation of wall structure and how wall components interact to provide strength. Consideration must be given to wall assembly as well as to wall disassembly. Furthermore, the apoplast must be considered as a developmentally and biochemically distinct, dynamic ,compartment', not just the location of the cell wall structural matrix. New analytical approaches for enhancing the ability to understand wall structure and metabolism are discussed. Fruit cells regulate their turgor pressure as well as cell wall integrity as they ripen, and it is proposed that future studies of fruit softening should include attempts to understand the bases of cell- and tissue-level turgor regulation if the goal of optimising softening control is to be reached. Finally, recent studies show that cell wall breakdown provides sugar substrates that fuel other important cellular pathways and processes. These connections must be explored so that optimisation of softening does not lead to decreases in other aspects of fruit quality. Copyright © 2007 Society of Chemical Industry [source] The novel herbicide oxaziclomefone inhibits cell expansion in maize cell cultures without affecting turgor pressure or wall acidificationNEW PHYTOLOGIST, Issue 2 2005Nichola O'Looney Summary ,,Oxaziclomefone [OAC; IUPAC name 3-(1-(3,5-dichlorophenyl)-1-methylethyl)-3,4-dihydro-6-methyl-5-phenyl-2H -1,3-oxazin-4-one] is a new herbicide that inhibits cell expansion in grass roots. Its effects on cell cultures and mode of action were unknown. In principle, cell expansion could be inhibited by a decrease in either turgor pressure or wall extensibility. ,,Cell expansion was estimated as settled cell volume; cell division was estimated by cell counting. Membrane permeability to water was measured by a novel method involving simultaneous assay of the efflux of 3H2O and [14C]mannitol from a ,bed' of cultured cells. Osmotic potential was measured by depression of freezing point. ,,OAC inhibited cell expansion in cultures of maize (Zea mays), spinach (Spinacia oleracea) and rose (Rosa sp.), with an ID50 of 5, 30 and 250 nm, respectively. In maize cultures, OAC did not affect cell division for the first 40 h. It did not affect the osmotic potential of cell sap or culture medium, nor did it impede water transport across cell membranes. It did not affect cells' ability to acidify the apoplast (medium), which may be necessary for ,acid growth'. ,,As OAC did not diminish turgor pressure, its ability to inhibit cell expansion must depend on changes in wall extensibility. It could be a valuable tool for studies on cell expansion. [source] Ozone-induced reductions in below-ground biomass: an anatomical approach in potatoPLANT CELL & ENVIRONMENT, Issue 7 2010AMPARO ASENSI-FABADO ABSTRACT Potato plants were grown in open-top chambers under three ozone concentrations during two complete cropping seasons (93 and 77 d in 2004 and 2005, respectively). The effects of chronic exposure to ozone on leaf anatomy, cell ultrastructure and crop yield were studied. Severe cell damage was found, even at ambient ozone levels, mainly affecting the spongy parenchyma and areas near the stomata. Damage to the cell wall caused loss of cell contact, and loss of turgor pressure due to tonoplast disintegration, contributed to cell collapse. Phloem sieve plates were obstructed by callose accumulation, and damaged mesophyll cells increased their starch stores. Tuber yield fell sharply (24,44%), due to the biggest tubers becoming smaller, which affected commercial yield. These anatomical findings show the mechanisms of ozone effect on assimilate partitioning, and thus crop yield decrease, in potato. Further implications of ozone causing reductions in below-ground biomass are also discussed. [source] The determination of membrane transport parameters with the cell pressure probe: theory suggests that unstirred layers have significant impactPLANT CELL & ENVIRONMENT, Issue 12 2005MELVIN T. TYREE ABSTRACT A simulation model was written to compute the time-kinetics of turgor pressure, P, change in Chara corallina during cell pressure probe experiments. The model allowed for the contribution of a membrane plus zero, one, or two unstirred layers of any desired thickness. The hypothesis that a cell with an unstirred layer is a composite membrane that will follow the same kind of kinetics with or without unstirred layers was tested. Typical ,osmotic pulse' experiments yield biphasic curves with minimum or maximum pressures, Pmin(max), at time tmin(max) and a solute exponential decay with halftime . These observed data were then used to compute composite membrane properties, namely the parameters Lp = the hydraulic conductance, , = reflection coefficient and Ps = solute permeability using theoretical equations. Using the simulation model, it was possible to fit an experimental data set to the same values of Pmin(max), tmin(max) and incorporating different, likely values of unstirred layer thickness, where each thickness requires a unique set of plasmalemma membrane values of Lp, , and Ps. We conclude that it is not possible to compute plasmalemma membrane properties from cell pressure probe experiments without independent knowledge of the unstirred layer thickness. [source] Turgor pressure, membrane tension and the control of exocytosis in higher plantsPLANT CELL & ENVIRONMENT, Issue 9 2000Wieland Fricke ABSTRACT Both turgor pressure and differences in membrane tension are capable of providing an energy input into exocytosis, the process of fusion of Golgi vesicles with the cell membrane in plants. It is shown that the contribution of turgor pressure is much larger than that of membrane tension, so that the exocytotic process is not likely on thermodynamic grounds to be reversible unless another source of energy is made available. However, recycling of membrane material as flattened, empty vesicles is energetically possible and is likely to be favoured when the magnitude of membrane tension in the cell membrane is low. Thus the outward flows of membrane and cell wall material are in principle linked to turgor, whereas membrane tension influences the inward flow of membrane material. [source] Remote monitoring of leaf turgor pressure of grapevines subjected to different irrigation treatments using the leaf patch clamp pressure probeAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 3 2010S. RÜGER Abstract Background and Aims:, Effects of four irrigation treatments on leaf turgor pressure of grapevines were studied using the novel leaf patch clamp pressure (LPCP) probe. Data were correlated with yield and yield components. Methods and Results:, The LPCP probe measures leaf water status by monitoring the attenuation of an external pressure applied magnetically to a leaf patch. The output pressure signals, Pp, are inversely correlated with cell turgor pressure. Measurements showed that changes in transpiration and stomatal conductance induced by environmental parameters were reflected nearly immediately in Pp. Ongoing non-irrigation resulted in a continuous increase of Pp, in the occurrence of stomatal oscillations and in an increased turgor pressure recovery phase during afternoon. Interestingly, analysis of the numerous diurnal Pp data sets showed that east-directed leaves responded more sensitively to water stress than west-directed leaves. Conclusions:, For the cultivar and conditions used in this study, the probe data as well as the yield data support irrigation on a 3-day basis with relatively small amounts of water. Significance of the Study:, The results show that the LPCP probe is a user-friendly, high precision instrument for online-monitoring of leaf turgor pressure in dependency on changes in microclimate and irrigation, thus helping growers to increase yield while simultaneously saving water. [source] | |||||||||||||||||||||||||