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Graham D Farquhar - One of the best experts on this subject based on the ideXlab platform.
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Measurement of guard Cell wall elasticity and implications for stomatal sensitivity to environmental stimuli
Science Access, 2001Co-Authors: Peter J. Franks, Thomas N Buckley, Keith A. Mott, Joseph C. Shope, Graham D FarquharAbstract:Over the course of stomatal opening guard Cells exhibit dramatic changes in volume. This dynamic characteristic is driven by changes in guard Cell osmotic Pressure and water potential, but constrained by the elastic properties of the guard Cell walls. Thus guard Cell wall elasticity will strongly influence the sensitivity of stomata to environmental stimuli. However, our understanding of guard Cell wall elastic properties is limited. In this study we calculated the elastic modulus e of guard Cells of Vicia faba L. by taking concurrent measurements of guard Cell volume and Pressure using confocal microscopy and a Cell Pressure probe. While controlling guard Cell Pressure at intervals over the range 0.3 to 5.0 MPa, guard Cell volume increased with Pressure in a saturating fashion and e increased linearly from approximately 2 to 40 MPa. These new data allow a quantitative understanding of the relationship between guard Cell osmotic content and stomatal conductance, with implications for stomatal responses to light, CO2 and humidity.
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A study of stomatal mechanics using the Cell Pressure probe
Plant Cell and Environment, 1998Co-Authors: Peter J. Franks, I.r. Cowan, Graham D FarquharAbstract:The relationship between stomatal aperture (a) and guard Cell Pressure (Pg) was measured directly in four different species (Vicia faba, Tradescantia virginiana, Ginkgo biloba and Nephrolepis exaltata) using a special Cell Pressure probe technique. The effect of epidermal turgor (Pep) on this relationship was also measured in T. virginiana. The relationship was sigmoidal for V. faba and T. virginiana, but entirely convex for G. biloba and N. exaltata. Epidermal turgor was found to have a pronounced closing effect on stomata of T. virginiana. Maximum aperture with full epidermal turgor (0·92 MPa) was about half that with zero epidermal turgor. Also, with full epidermal turgor stomata of T. virginiana did not begin to open until Pg was more than 1·25 MPa. These characteristics were used to develop an expression for a as a function of Pg and Pep. Results for the different species are compared and discussed in terms of possible advantages and limitations of water economy.
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Guard Cell Pressure/aperture characteristics measured with the Pressure probe
Plant Cell and Environment, 1995Co-Authors: Peter J. Franks, I.r. Cowan, Stephen D Tyerman, A. L. Cleary, Jon Lloyd, Graham D FarquharAbstract:Pressure within guard Cells in strips of intact epidermis of Tradescantia virginiana was controlled with a Pressure probe apparatus after the guard Cells had been filled with silicone oil. Pressure was increased and decreased incrementally between 0.0 and 4.1 MPa to cause inflation and deflation of the guard Cells. At steady-state guard Cell Pressures, the width of the stomatal pore was recorded and plotted against Pressure. The Pressure required for near-maximum aperture was 4.1 MPa. Aperture as a function of Pressure was sigmoidal.
Peter J. Franks - One of the best experts on this subject based on the ideXlab platform.
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Guard Cell Volume and Pressure Measured Concurrently by Confocal Microscopy and the Cell Pressure Probe
Plant physiology, 2001Co-Authors: Peter J. Franks, Thomas N Buckley, Joseph C. Shope, Keith A. MottAbstract:Guard Cell turgor Pressures in epidermal peels of broad bean (Vicia faba) were measured and controlled with a Pressure probe. At the same time, images of the guard Cell were acquired using confocal microscopy. To obtain a clear image of guard Cell volume, a fluorescent dye that labels the plasma membrane was added to the solution bathing the epidermal peel. At each Pressure, 17 to 20 optical sections (each 2 μm thick) were acquired. Out-of-focus light in these images was removed using blind deconvolution, and volume was estimated using direct linear integration. As Pressure was increased from as low as 0.3 MPa to as high as 5.0 MPa, guard Cell volume increased in a saturating fashion. The elastic modulus was calculated from these data and was found to range from approximately 2 to 40 MPa. The data allow inference of guard Cell osmotic content from stomatal aperture and facilitate accurate mechanistic modeling of epidermal water relations and stomatal functioning.
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Measurement of guard Cell wall elasticity and implications for stomatal sensitivity to environmental stimuli
Science Access, 2001Co-Authors: Peter J. Franks, Thomas N Buckley, Keith A. Mott, Joseph C. Shope, Graham D FarquharAbstract:Over the course of stomatal opening guard Cells exhibit dramatic changes in volume. This dynamic characteristic is driven by changes in guard Cell osmotic Pressure and water potential, but constrained by the elastic properties of the guard Cell walls. Thus guard Cell wall elasticity will strongly influence the sensitivity of stomata to environmental stimuli. However, our understanding of guard Cell wall elastic properties is limited. In this study we calculated the elastic modulus e of guard Cells of Vicia faba L. by taking concurrent measurements of guard Cell volume and Pressure using confocal microscopy and a Cell Pressure probe. While controlling guard Cell Pressure at intervals over the range 0.3 to 5.0 MPa, guard Cell volume increased with Pressure in a saturating fashion and e increased linearly from approximately 2 to 40 MPa. These new data allow a quantitative understanding of the relationship between guard Cell osmotic content and stomatal conductance, with implications for stomatal responses to light, CO2 and humidity.
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A study of stomatal mechanics using the Cell Pressure probe
Plant Cell and Environment, 1998Co-Authors: Peter J. Franks, I.r. Cowan, Graham D FarquharAbstract:The relationship between stomatal aperture (a) and guard Cell Pressure (Pg) was measured directly in four different species (Vicia faba, Tradescantia virginiana, Ginkgo biloba and Nephrolepis exaltata) using a special Cell Pressure probe technique. The effect of epidermal turgor (Pep) on this relationship was also measured in T. virginiana. The relationship was sigmoidal for V. faba and T. virginiana, but entirely convex for G. biloba and N. exaltata. Epidermal turgor was found to have a pronounced closing effect on stomata of T. virginiana. Maximum aperture with full epidermal turgor (0·92 MPa) was about half that with zero epidermal turgor. Also, with full epidermal turgor stomata of T. virginiana did not begin to open until Pg was more than 1·25 MPa. These characteristics were used to develop an expression for a as a function of Pg and Pep. Results for the different species are compared and discussed in terms of possible advantages and limitations of water economy.
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Guard Cell Pressure/aperture characteristics measured with the Pressure probe
Plant Cell and Environment, 1995Co-Authors: Peter J. Franks, I.r. Cowan, Stephen D Tyerman, A. L. Cleary, Jon Lloyd, Graham D FarquharAbstract:Pressure within guard Cells in strips of intact epidermis of Tradescantia virginiana was controlled with a Pressure probe apparatus after the guard Cells had been filled with silicone oil. Pressure was increased and decreased incrementally between 0.0 and 4.1 MPa to cause inflation and deflation of the guard Cells. At steady-state guard Cell Pressures, the width of the stomatal pore was recorded and plotted against Pressure. The Pressure required for near-maximum aperture was 4.1 MPa. Aperture as a function of Pressure was sigmoidal.
Arezki Boudaoud - One of the best experts on this subject based on the ideXlab platform.
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Gradient in cytoplasmic Pressure in germline Cells controls overlying epithelial Cell morphogenesis
PLoS Biology, 2020Co-Authors: Laurie-anne Lamiré, Pascale Milani, Gaël Runel, Annamaria Kiss, Leticia Arias, Blandine Vergier, Stève De Bossoreille, Pradeep Das, David Cluet, Arezki BoudaoudAbstract:It is unknown how growth in one tissue impacts morphogenesis in a neighboring tissue. To address this, we used the Drosophila ovarian follicle, in which a cluster of 15 nurse Cells and a posteriorly located oocyte are surrounded by a layer of epithelial Cells. It is known that as the nurse Cells grow, the overlying epithelial Cells flatten in a wave that begins in the anterior. Here, we demonstrate that an anterior to posterior gradient of decreasing cytoplasmic Pressure is present across the nurse Cells and that this gradient acts through TGFβ to control both the triggering and the progression of the wave of epithelial Cell flattening. Our data indicate that intrinsic nurse Cell growth is important to control proper nurse Cell Pressure. Finally, we reveal that nurse Cell Pressure and subsequent TGFβ activity in the stretched Cells combine to increase follicle elongation in the anterior, which is crucial for allowing nurse Cell growth and Pressure control. More generally, our results reveal that during development, inner cytoplasmic Pressure in individual Cells has an important role in shaping their neighbors.
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a mechanical model to interpret Cell scale indentation experiments on plant tissues in terms of Cell wall elasticity and turgor Pressure
Frontiers in Plant Science, 2016Co-Authors: Francois Faure, Richard Malgat, Arezki BoudaoudAbstract:Morphogenesis in plants is directly linked to the mechanical elements of growing tissues, namely Cell wall and inner Cell Pressure. Studies of these structural elements are now often performed using indentation methods such as atomic force microscopy. In these methods, a probe applies a force to the tissue surface at a subCellular scale and its displacement is monitored, yielding force-displacement curves that reflect tissue mechanics. However, the interpretation of these curves is challenging as they may depend not only on the Cell probed, but also on neighboring Cells, or even on the whole tissue. Here, we build a realistic three-dimensional model of the indentation of a flower bud using SOFA (Simulation Open Framework Architecture), in order to provide a framework for the analysis of force-displacement curves obtained experimentally. We find that the shape of indentation curves mostly depends on the ratio between Cell Pressure and wall modulus. Hysteresis in force-displacement curves can be accounted for by a viscoelastic behavior of the Cell wall. We consider differences in elastic modulus between Cell layers and we show that, according to the location of indentation and to the size of the probe, force-displacement curves are sensitive with different weights to the mechanical components of the two most external Cell layers. Our results confirm most of the interpretations of previous experiments and provide a guide to future experimental work.
Richard Malgat - One of the best experts on this subject based on the ideXlab platform.
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a mechanical model to interpret Cell scale indentation experiments on plant tissues in terms of Cell wall elasticity and turgor Pressure
Frontiers in Plant Science, 2016Co-Authors: Francois Faure, Richard Malgat, Arezki BoudaoudAbstract:Morphogenesis in plants is directly linked to the mechanical elements of growing tissues, namely Cell wall and inner Cell Pressure. Studies of these structural elements are now often performed using indentation methods such as atomic force microscopy. In these methods, a probe applies a force to the tissue surface at a subCellular scale and its displacement is monitored, yielding force-displacement curves that reflect tissue mechanics. However, the interpretation of these curves is challenging as they may depend not only on the Cell probed, but also on neighboring Cells, or even on the whole tissue. Here, we build a realistic three-dimensional model of the indentation of a flower bud using SOFA (Simulation Open Framework Architecture), in order to provide a framework for the analysis of force-displacement curves obtained experimentally. We find that the shape of indentation curves mostly depends on the ratio between Cell Pressure and wall modulus. Hysteresis in force-displacement curves can be accounted for by a viscoelastic behavior of the Cell wall. We consider differences in elastic modulus between Cell layers and we show that, according to the location of indentation and to the size of the probe, force-displacement curves are sensitive with different weights to the mechanical components of the two most external Cell layers. Our results confirm most of the interpretations of previous experiments and provide a guide to future experimental work.
Peter Sands - One of the best experts on this subject based on the ideXlab platform.
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The determination of membrane transport parameters with the Cell Pressure probe: theory suggests that unstirred layers have significant impact
Plant Cell and Environment, 2005Co-Authors: Melvin T. Tyree, Sharon Koh, Peter SandsAbstract: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, P min(max) , at time t min(max) and a solute exponential decay with halftime T 1/2 , These observed data were then used to compute composite membrane properties, namely the parameters L P = the hydraulic conductance, σ= reflection coefficient and P s = solute permeability using theoretical equations. Using the simulation model, it was possible to fit an experimental data set to the same values of P min(max) , t min(max) and T 1/2 incorporating different, likely values of unstirred layer thickness, where each thickness requires a unique set of plasmalemma membrane values of L p , or and P,. 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.