Direct measurement of negative pressure in artificial-biological systems

Balling, A.; Zimmermann, U.; Büchner, Karl-Heinz; Lange, O. L.

doi:10.1007/bf00377819

Cited by 42 publications

(31 citation statements)

References 5 publications

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“…The pressure can be calculated from the voltage after appropriate calibration. Accurate determination of turgor pressure and of the changes in it require control of the position of the cell sap-oil boundary by manual or electronic means (Hfisken et al 1978;Biichner et al 1987;Balling et al 1988). This is achieved by displacement of a metal rod within the pressure probe sealed to the methacrylate glass chamber.…”

Section: Methodsmentioning

confidence: 99%

“…For the studies with the Hepp-type bio-osmometer (Balling et al 1988 and see below) plants of Plantago major L. or P. lanceolata L., taken from the botanical garden in W/irzburg, were used.…”

Section: Methodsmentioning

confidence: 99%

“…The only approach to the problem seems to be direct measurements of the tension within the xylem. Recently, by using a "Hepp-type bio-osmometer" (Balling et al 1988), we have shown that the pressure probe originally developed for the measurements of turgor pressure in plant cells (Zimmermann et al 1969;Zimmermann and Steudle 1978;Zimmermann , 1989 can accurately read tensions in the intact xylem.…”

Section: Introductionmentioning

confidence: 99%

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Comparative measurements of the xylem pressure ofNicotiana plants by means of the pressure bomb and pressure probe

Balling

Zimmermann

1990

Planta

137

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Determination of the pressure in the water-conducting vessels of intactNicotiana rustica L. plants showed that the pressure probe technique gave less-negative values than the Scholander-bomb method. Even though absolute values of the order of -0.1 MPa could be directly recorded in the xylem by means of the pressure probe, pressures between zero and atmospheric were also frequently found. The data obtained by the pressure probe for excised leaves showed that the Scholander bomb apparently did not read the actual tension in the xylem vessles ofNicotiana plants. The possibility that the pressure probe gave false readings was excluded by several experimental controls. In addition, cavitation and leaks either during the insertion of the microcapillary of the pressure probe, or else during the measurements were easily recognized when they occurred because of the sudden increase of the absolute xylem tension to that of water vapour or to atmospheric, respectively. Tension values of the same order could also be measured by means of the pressure probe in the xylem vessels of pieces of stem cut from leaves and roots under water and clamped at both ends. The magnitude of the absolute tension depended on the osmolarity of the bathing solution which was adjusted by addition of appropriate concentrations of polyethylene glycol. Partial and uniform pressurisation of plant tissues or organs, or of entire plants (by means of the Scholander bomb or of a hyperbaric chamber, respectively) and simultaneous recording of the xylem tension using the pressure probe showed that a 1∶1 response in xylem pressure only occurred under a few circumstances. A 1∶1 response required that the xylem vessels were in direct contact with an external water reservoir and/or that the tissue was (pre-)infiltrated with water. Corresponding pressure-probe measurements in isolated vascular bundles ofPlantago major L. orP. lanceolata L. plants attached to a Hepp-type osmometer indicated that the magnitude of the tension in the xylem vessels was determined by the external osmotic pressure of the reservoir. These and other experiments, as well as analysis of the data using classical thermodynamics, indicated that the turgor and the internal osmotic pressure of the accessory cells along the xylem vessels play an important role in the maintenance of a constant xylem tension. This conclusion is consistent with the cohesion theory. In agreement with the literature (P.E. Weatherley, 1976, Philos. Trans. R. Soc. London Ser. B23, 435-444; 1982, Encyclopedia of plant physiology, vol. 12B, 79-109), it was found that the tension in the xylem of intact plants under normal and elevated ambient pressure (as measured with the pressure probe) under quasi-stationary conditions was independent of the transpiration rate over a large range, indicating that the conductance of the flow path must be flow-dependent.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparative measurements of the xylem pressure ofNicotiana plants by means of the pressure bomb and pressure probe

Balling

Zimmermann

1990

Planta

137

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“…Steudle and Heydt (1988) developed an artificial osmotic cell for studying phenomena of negative pressure in plants. The pressure-probe techtiique was used to record direct measurements of negative turgor, which was artificially generated on individual cells in glass capillaries (Balling et al 1988). The miniaturized cellular pressure probe is the only method available for direct measurement of ttirgor in cells of higher plants (Husken et al 1978); a new probe monitoring eel!…”

Section: Uncertaintymentioning

confidence: 99%

Is negative turgor fallacious?

Rhizopoulou¹

1997

Physiologia Plantarum

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Rhizopoulou, S. 1997. Is negative turgor fallacious? -Physiol. Plant 99: 505-510.In early studies, negative turgor pressure was obtained by indirect methods and was mainly related to inaccurate measurements of osmotic and/or water potential. The uncertainties in the measurements made any discussion of the underlying reasons and phenomena premature and risky, perhaps even useless. Yet, the idea of relating negative turgor to the strength of small-sized cells with thick walls, to resist collapse when subjected to water deficit, seemed attractive. Negative turgor pressures are difficult to detect in higher plants, but they are theoretically possible. Regarding their origin, a hypothesis is discussed here, that the negative turgor detected in leaves might indicate a reversal of the water flow that has occurred in roots, under conditions of severe and prolonged drought.

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“…4). For osmotic generation of defined tensions in a fluid and calibration of the xylem pressure probe, the reader is referred to Balling et al (1988), where the use of a Hepp-type osmometer is described.…”

mentioning

confidence: 99%