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Titolo:
DETERMINATION OF CELL WATER-RELATION PARAMETERS USING THE PRESSURE PROBE - EXTENDED THEORY AND PRACTICE OF THE PRESSURE-CLAMP TECHNIQUE
Autore:
MURPHY R; SMITH JAC;
Indirizzi:
UNIV DELAWARE,COLL MARINE STUDIES,700 PILOTTOWN RD LEWES DE 19958 UNIV OXFORD,DEPT PLANT SCI OXFORD OX1 3RB ENGLAND
Titolo Testata:
Plant, cell and environment
fascicolo: 7, volume: 21, anno: 1998,
pagine: 637 - 657
SICI:
0140-7791(1998)21:7<637:DOCWPU>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
CRASSULACEAN ACID METABOLISM; HIGHER-PLANT CELLS; KALANCHOE-DAIGREMONTIANA; TURGOR PRESSURE; HYDRAULIC CONDUCTIVITY; ELECTRICAL-RESISTANCE; COMPARTMENT ANALYSIS; WHEAT ROOTS; PLASMODESMATA; MEMBRANES;
Keywords:
KALANCHOE DAIGREMONTIANA; MEMBRANE TRANSPORT; PLASMODESMATA; PRESSURE CLAMP; PRESSURE PROBE; WATER RELATIONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
59
Recensione:
Indirizzi per estratti:
Citazione:
R. Murphy e J.A.C. Smith, "DETERMINATION OF CELL WATER-RELATION PARAMETERS USING THE PRESSURE PROBE - EXTENDED THEORY AND PRACTICE OF THE PRESSURE-CLAMP TECHNIQUE", Plant, cell and environment, 21(7), 1998, pp. 637-657

Abstract

The aim of tbe present study was to develop and test an extended theory of the pressure-clamp technique that would allow the estimation of additional cell water-relation parameters using the pressure probe. Itwas assumed that intercellular water transport (vacuole --> vacuole) occurs via a composite 'membrane' comprising the tonoplast, cytoplasm,plasma membrane, plasmodesmata and cell mall and that solute transport across the micropipette tip of the probe is dominated by convection. The extended theory allows the simultaneous estimation of cell volume(V), effective cell-sap osmotic pressure (sigma Pi(0)), composite-membrane hydraulic conductance (AL(P)) and the 'instantaneous' volume change (nu(0)) at the start of the pressure clamp, With an estimate of cell-sap osmotic pressure (Pi(0)), the weighted-average reflection coefficient (sigma) of the composite membrane may also be determined from an endosmotic pressure-clamp experiment. In principle, the cell volume before the clamp (V-0) can be estimated as V-0 = V + nu(0), and the cell volumetric elastic modulus (epsilon) can be estimated as epsilon = -V-0(Delta P/nu(0)), where Delta P (< 0) is the change in turgor pressure at t = 0, In practice it may be necessary to correct nu(0) for transmembrane water flow when estimating V-0 and epsilon. To test this theory, a previously described pressure-probe system was upgraded by incorporating a data-acquisition system to record turgor pressure, meniscus position, the penetration depth of the pressure-probe micropipette and the micropipette profile. An air bubble in the system allowed the turgor pressure to be clamped at a near-constant value, For mesophyll cells in Leaf discs of Kalanchoe; daigremontiana, the estimated mean value of V-0 [(2.46 +/- 0.24) x 10(-13) m(3)] was in reasonable agreement with a value obtained from microscopy [(1.91 +/- 0.10) x 10(-13) m(3)]. When the positive correlation between epsilon and \Delta P\ was taken into account, the parameter estimates obtained from pressure-clamp experiments were found to be consistent with those derived from pressure-relaxation experiments. The mean values of epsilon (1.4 +/- 0.2 MPa) and L-P [(5.76 +/- 0.83) x 10(-12) m s(-1) Pa-1] were significantly different from previous estimates obtained with older leaves, Furthermore, in contrast to the estimated reflection coefficient of the plasma membrane/tonoplast (approximate to 1), the mean value of a obtainedin the present study (0.62 +/- 0.05) was significantly less than unity. This is attributed to a high hydraulic conductance and a low reflection coefficient of a symplastic pathway for intercellular water transport. The qualitative behaviour of L-P and sigma was consistent with aquasi-steady-state model of intercellular water transport that included volume flow through plasmodesmata, A quantitative description was obtained by fitting a simplified version of this model to the data. This led to the conclusion that significant volume flow can occur throughplasmodesmata during pressure-clamp experiments, especially for smallA and \Delta P\.

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Documento generato il 23/10/20 alle ore 14:31:02