On the Theory of Osmotic Water Movement

Ray, Peter M.

doi:10.1104/pp.35.6.783

Cited by 83 publications

(40 citation statements)

References 45 publications

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“…The possible existence of water-transporting pores or water channels in membranes of higher plants was discussed nearly 40 years ago (7,8). However, experimental approaches to the molecular mechanisms of membrane water permeability in these organisms have been rare until recently (6), and the diffusion of water molecules across the lipid matrix was generally considered sufficient to account for transmembrane water exchange.…”

Section: Introductionmentioning

confidence: 99%

“…However, this technique only provides access to the overall cell hydraulic conductivity that includes the water permeabilities of the PM and the TP plus those of the cell wall and the plasmodesmata. The individual water permeabilities of the two membranes thus remain to be determined in these cells (6).The possible existence of water-transporting pores or water channels in membranes of higher plants was discussed nearly 40 years ago (7,8). However, experimental approaches to the molecular mechanisms of membrane water permeability in these organisms have been rare until recently (6), and the diffusion of water molecules across the lipid matrix was generally considered sufficient to account for transmembrane water exchange.…”

mentioning

confidence: 99%

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Purified vesicles of tobacco cell vacuolar and plasma membranes exhibit dramatically different water permeability and water channel activity

Maurel

Tacnet²,

Güçlü³

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

170

137

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The vacuolar membrane or tonoplast (TP) and the plasma membrane (PM) of tobacco suspension cells were purified by free-f low electrophoresis (FFE) and aqueous two-phase partitioning, with enrichment factors from a crude microsomal fraction of >4-to 5-fold and reduced contamination by other cellular membranes. For each purified fraction, the mean apparent diameter of membrane vesicles was determined by freeze-fracture electron microscopy, and the osmotic shrinking kinetics of the vesicles were characterized by stopped-f low light scattering. Osmotic water permeability coefficients (P f ) of 6.1 ؎ 0.2 and 7.6 ؎ 0.9 m⅐s ؊1 were deduced for PM-enriched vesicles purified by FFE and phase partitioning, respectively. The associated activation energies (E a ; 13.7 ؎ 1.0 and 13.4 ؎ 1.4 kcal⅐mol ؊1 , respectively) suggest that water transport in the purified PM occurs mostly by diffusion across the lipid matrix. In contrast, water transport in TP vesicles purified by FFE was characterized by (i) a 100-fold higher P f of 690 ؎ 35 m⅐s ؊1 , (ii) a reduced E a of 2.5 ؎ 1.3 kcal⅐mol ؊1 , and (iii) a reversible inhibition by mercuric chloride, up to 83% at 1 mM. These results provide functional evidence for channel-mediated water transport in the TP, and more generally in a higher plant membrane. A high TP P f suggests a role for the vacuole in buffering osmotic f luctuations occurring in the cytoplasm. Thus, the differential water permeabilities and water channel activities observed in the tobacco TP and PM point to an original osmoregulatory function for water channels in relation to the typical compartmentation of plant cells.In plants, the cell wall continuum and the cell-to-cell communications (plasmodesmata) provide privileged paths for water exchange and equilibration. Cellular membranes also critically control water transport in a variety of functions, including cell volume and turgor regulation and long-distance transport in nonvascular tissues (1). These functions involve the ability of membranes to transport or sequester osmotic solutes as well as their intrinsic permeability to water (1, 2). The presence in most plant cells of a large vacuole suggests that intra-and transcellular water exchange may depend on the permeability of two membranes in series, the plasma membrane (PM) and the vacuolar membrane or tonoplast (TP) (3, 4). Pressure probe measurements have brought about a better understanding of water relations in a variety of higher plant cell types (1, 5). However, this technique only provides access to the overall cell hydraulic conductivity that includes the water permeabilities of the PM and the TP plus those of the cell wall and the plasmodesmata. The individual water permeabilities of the two membranes thus remain to be determined in these cells (6).The possible existence of water-transporting pores or water channels in membranes of higher plants was discussed nearly 40 years ago (7,8). However, experimental approaches to the molecular mechanisms of membrane water permeability in these organisms h...

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Purified vesicles of tobacco cell vacuolar and plasma membranes exhibit dramatically different water permeability and water channel activity

Maurel

Tacnet²,

Güçlü³

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

170

137

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“…Diffusion at pore openings may also govern mass flow as suggested recently by Ray (9). In the case of 'r )nporous membranes all of the mass flowv permeabilm-111ight be nmeasured by diffusive permeability.…”

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confidence: 99%

Diffusion of tritiated water into roots as influenced by water status of tissue

Ordin¹,

Gairon²

1961

Plant Physiol.

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“…Note that this 'total pressure' is a classical concept, see Mauro, 45 Ray 46 and the 'solvent partial pressure' in Osterle. 4,5 In many situations we can neglect Π such as for non-colloidal suspensions of large particles and/or when non-osmotic forces are much larger, but when we make this assumption in general, then the physics of many classical problems cannot be explained, such as osmosis, the phenomenon where fluid moves against a hydraulic pressure gradient toward locations of higher osmotic pressure, Π.…”

mentioning

confidence: 99%

“…Thus, with ∆χ -the solvation energy increase for a particle to enter the membrane-positive, we have 0<S<1, i.e., the concentration of particles just within the membrane is lower than in the adjacent solution, which results in a decrease both in the osmotic and hydraulic pressure upon entering the membrane (with the total pressure P t remaining constant across the interface). 1,7,8,46 Within the membrane, χ is constant and we can integrate Eq. (1) across the membrane to obtain 1,8,53…”

mentioning

confidence: 99%

Two-fluid model for the simultaneous flow of colloids and fluids in porous media

Biesheuvel

2011

Journal of Colloid and Interface Science

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On the Theory of Osmotic Water Movement

Cited by 83 publications

References 45 publications

Purified vesicles of tobacco cell vacuolar and plasma membranes exhibit dramatically different water permeability and water channel activity

Purified vesicles of tobacco cell vacuolar and plasma membranes exhibit dramatically different water permeability and water channel activity

Diffusion of tritiated water into roots as influenced by water status of tissue

Two-fluid model for the simultaneous flow of colloids and fluids in porous media

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