The Osmotic Cell, Solute Diffusibility, and the Plant Water Economy.

Philip, J. R.

doi:10.1104/pp.33.4.264

Cited by 134 publications

(53 citation statements)

References 16 publications

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“…The nature of this resistance is not known but it may be due to air gaps between the soil and root, resulting in a paucity of points of contract between the soil particles and the root surface. The possible occurrence of such gaps was first suggested by Philip (1957Philip ( , 1958 and Bonner (1959). The gaps might occur through the growing roots traversing soil voids and fissures of greater dimensions than those of the roots themselves, or they may result from shrinkage of the roots arising from water stress in the plants (Tinker, 1976).…”

Section: Introductionmentioning

confidence: 99%

Root Contraction in Transpiring Plants

Faiz

Weatherley

1982

New Phytologist

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SUMMARY Experimental data published previously (Faiz and Weatherley, 1977) emphasized the existence of considerable hydraulic resistance in the perirhizal soil of rapidly transpiring plants. This was evident when soil water potential (Ψs in the root zone was as high as −2 or −3 bars. In a further paper (Faiz and Weatherley, 1978) the hypothesis was put forward that it is the soil‐root interface which presents a high resistance to the flow of water through the soil‐plant system. This resistance, it was thought, could increase as a result of contraction of stressed‐roots, with the formation of vapour gaps between soil and root. In this paper we demonstrate that the root tissues may contract by as much as 25 % of their turgid volume when the water potential of the leaves (Ψl) falls to around −15 bars. Under such conditions the extensive formation of vapour gaps would be expected and a reduction of water stress should therefore follow if the gaps could be closed mechanically. Such closure was attempted by either squeezing or vibrating the soil mass containing the root system. Both of these treatments led to a temporary reduction in water stress in the plants and the existence of vapour gaps was thus supported.

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Section: Introductionmentioning

confidence: 99%

Root Contraction in Transpiring Plants

Faiz

Weatherley

1982

New Phytologist

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“…The modulus of elasticity describes the dependence of cell volume on pressure: DP5e? (DV/V i ) (Philip, 1958;Husken et al, 1978). In the case of the relation between turgor and relative hyphal volume per unit length (Fig.…”

Section: Time-course Of Hyperosmotic-induced Hyphal Changesmentioning

confidence: 99%

Transient responses during hyperosmotic shock in the filamentous fungus Neurospora crassa

Lew

Nasserifar

2009

Microbiology

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Fungal cells maintain an internal hydrostatic pressure (turgor) of about 400-500 kPa. In the filamentous fungus Neurospora crassa, the initial cellular responses to hyperosmotic treatment are loss of turgor, a decrease in relative hyphal volume per unit length (within 1 min) and cell growth arrest; all recover over a period of 10-60 min due to increased net ion uptake and glycerol production. The electrical responses to hyperosmotic treatment are a transient depolarization of the potential (within 1 min), followed by a sustained hyperpolarization (after 4 min) to a potential more negative than the initial potential (a driving force for ion uptake). The nature of the transient depolarization was explored in the context of other transient responses to hyperosmotic shock, to determine whether activation of a specific ion permeability or some other rapid change in electrogenic transport was responsible. Changing the ionic composition of the extracellular medium revealed that K + permeability increases and H + permeability declines during the transient depolarization. We suggest that these changes are due to concerted inhibition of the electrogenic H + -ATPase, and an increase in a K + conductance. Knockout mutants of known K + (tok, trk, trm-8, hak-1) and Cl " (a clc-3 homologue) channels and transporters had no effect on the transient depolarization, but trk and hak-1 do play a role in osmoadaptation, as does a homologue of a serine kinase regulator of H + -ATPase in yeast, Ptk2.

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“…PT (1 (21) Here, eo refers to the membrane thickness when the electric field is zero (but the turgor pressure is present; see also Appendix A). 4 That is, deformation in the plane of the membrane and normal to the plane of the membrane are likely to be related by different elastic moduli to the deformation stresses.…”

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confidence: 99%

Turgor Pressure Sensing in Plant Cell Membranes

Coster

Steudle²,

Zimmermann³

1976

Plant Physiol.

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Experimental evidence is reviewed which shows that the cell membrane is compressible by both mechanical and electrical forces. Calculations are given which show that significant changes in the thickness of cell membranes can occur as a result of (a) direct compression due to the turgor pressure; (b) indirect effects due to the stretching of the cell wail; and (c) the stresses induced by the electric field in the membrane.Such changes in the membrane thickness may provide the pressuretransducing mechanism required for osmoregulation and growth. An important feature of the model is that this pressure transduction can occur not only in the plasmalemma (where there is a pressure gradient), but also in the tonoplast.ELASTIC FORCES IN CELL MEMBRANES Transverse Stresses. The over-all compressibility and dimensional stability of a cell membrane reflects the intermolecular forces operating in this structure. Although details of the molecular architecture and forces operating are still not known, the dimensions (thickness) of the membrane must, nevertheless, reflect external forces operating on it.When turgor pressure (PT) is applied to the membrane, internal strain (restoring) forces are set up. For a membrane or membrane segment, which need not necessarily be structurally homogeneous, the mechanical restoring force (Pm), per unit area, is given byThe regulation of turgor pressure in plant cells plays a vital role in both cell growth and homeostasis. Although this has been the subject of many studies (1,2,12,14,15,17,19,25,27,29,31), the mechanisms by which turgor pressure information is sensed and utilized in osmoregulation and growth remain unknown.Some experimental studies have revealed a relationship between the turgor pressure and membrane potential and resistance as well as a regulating effect on the osmotic pressure of the cell sap and actively transported ion fluxes (13-15, 27, 29, 31, 38).If one considers the cell membrane as a compressible structure, it seems likely that elastic deformation of the membrane or segments thereof in the plane normal to the membrane might play a role in the dependence of membrane properties on turgor pressure. Dielectric breakdown measurements on plant cell membranes, and particularly, the effect of turgor pressure on dielectric breakdown, have revealed that electromechanical forces operating in the membrane can lead to a reduction in membrane thickness (9,33,34).In this communication, we present considerations of the elastic deformation of cell membranes and its possible role in the turgor-sensing mechanism of plant cells.

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The Osmotic Cell, Solute Diffusibility, and the Plant Water Economy.

Cited by 134 publications

References 16 publications

Root Contraction in Transpiring Plants

Root Contraction in Transpiring Plants

Transient responses during hyperosmotic shock in the filamentous fungus Neurospora crassa

Turgor Pressure Sensing in Plant Cell Membranes

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