Simultaneous recording of xylem pressure and trans‐root potential in roots of intact glycophytes using a novel xylem pressure probe technique

Wegner, Lars H.; Zimmermann, U.

doi:10.1046/j.1365-3040.1998.00335.x

Cited by 42 publications

(64 citation statements)

References 71 publications

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“…in the liana T. voinierianum, Benkert et al, 1995 ;Zimmermann et al, 1995a,b ;Thu$ rmer et al, 1999 ;and in sugarcane and crop plants, F. Thu$ rmer et al, unpublished data ;Schneider et al, 1997a,b ;Wegner & Zimmermann, 1998).…”

Section: mentioning

confidence: 99%

Diurnal changes in xylem pressure of the hydrated resurrection plant Myrothamnus flabellifolia: evidence for lipid bodies in conducting xylem vessels

et al. 1999

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The resurrection plant Myrothamnus flabellifolia has the ability to recover from repeated prolonged and extreme desiccation cycles. During the dry state the inner walls of the xylem vessels seemed to be covered, at least partly, by a lipid film as shown by Sudan III and Nile Red staining. The lipid film apparently functioned as an ' internal cuticle ' which prevented the adjacent parenchyma ray cells from complete water loss. The hydrophobic nature of the inner xylem walls was supported by the finding that benzene ascended as rapidly as water in the xylem of dry Myrothamnus branches. On watering, numerous lipid bodies were found in the water-conducting vessels, presumably formed from the lipid film and\or from lipids excreted from the adjacent living cells into the vessels. The presence of lipid bodies within the vessels, as well as the hydrophobic properties of the inner xylem walls, could explain the finding that the xylem pressure of hydrated, well watered plants (measured both under laboratory and field conditions with the xylem pressure probe) never dropped below c. k0.3 MPa and that cavitation occurred frequently at low negative xylem pressure values (k0.05 to k0.15 MPa). The xylem pressure of M. flabellifolia responded rapidly and strongly to changes in relative humidity and temperature, but less obviously to changes in irradiance (which varied between 10 and c. 4000 µmol m −# s −" ). The morphological position of the stomata in the leaves could explain the extremely weak and slow response of the xylem pressure of this resurrection plant to illumination changes. Stomata were most abundant in the furrows, and were thus protected from direct sunlight. Simultaneous measurements of the cell turgor pressure in the leaf epidermal cells (made by using the cell turgor pressure probe) revealed that the xylem and the cell turgor pressure dropped in a ratio of 1 : 0.7 on changes in the environmental parameters, indicating a quite close hydraulic connection and, thus, water equilibrium between the xylem and cellular compartments. An increase in irradiance of c. 700 µmol m −# s −" resulted in a turgor pressure decrease from 0.63 to 0.48 MPa. Correspondingly, the cell osmotic pressure increased from 1.03 to 1.22 MPa. From these values and by assuming water equilibrium, the osmotic pressure of the xylem sap was estimated to be 0.25-0.4 MPa. This value seems to be fairly high but may, however, be explained by the reduction of the water volume within the vessels due to the floating lipid bodies.

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Section: mentioning

confidence: 99%

Diurnal changes in xylem pressure of the hydrated resurrection plant Myrothamnus flabellifolia: evidence for lipid bodies in conducting xylem vessels

et al. 1999

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“…The osmotic pressure remained constant during each perfusion experiment. This is important to note because a change in the osmotic pressure of the medium affects both xylem pressure and TRP (Zhu et al 1995;Schneider et al 1997;Wegner & Zimmermann 1998).…”

Section: Xylem Pressure and Trpmentioning

confidence: 99%

“…The conflicting data about the electrical coupling of root cells summarized above called for a re-evaluation of the relationship of cortical membrane potentials and the TRP in intact, transpiring plants by using the xylem pressure-potential probe described recently by Wegner & Zimmermann (1998).This probe is based on the xylem pressure probe developed by Balling & Zimmermann (1990) and allows the simultaneous recording of the xylem pressure and of the electrical potential in a root xylem vessel relative to the ambient medium. Monitoring of the pressure indicates precise placement of the tip of the capillary in a xylem vessel.…”

Section: Introductionmentioning

confidence: 99%

Trans‐root potential, xylem pressure, and root cortical membrane potential of ‘low‐salt’ maize plants as influenced by nitrate and ammonium

Wegner

Sattelmacher

Läuchli

et al. 1999

Plant Cell & Environment

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Upon addition of nitrate and ammonium, respectively, to the bath of intact 'low salt' maize plants, the cortical membrane potential and the trans-root potential changed in a similar and synchronous way as revealed by applying conventional microelectrode techniques and the xylem pressure-potential probe (Wegner & Zimmermann 1998). Upon addition of nitrate, a hyperpolarization response was observed which was frequently preceded by a short depolarization phase. In contrast, addition of ammonium resulted in an overall depolarization response both of the cortical membrane potential and the trans-root potential. The nitrate-induced hyperpolarization response and the depolarization following the addition of ammonium were concentration-dependent.The data suggest that a tight electrical coupling exists between the cellular and tissue level in the root of the intact plant and that the resistance of the cellular (symplastic) space is much less than the resistance of the apoplast.

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“…Maize seedlings (Zea mays L. cv Bangui) were cultured on hydroponics as described previously (Wegner and Zimmermann, 1998). Experiments were performed on 12-to 26-d-old plants.…”

Section: Plant Materialsmentioning

confidence: 99%

“…Both probes are based on the same measuring principle: a xylem vessel is impaled with a double-barreled, single-tipped microcapillary. One barrel is connected to a xylem pressure-potential probe (Wegner and Zimmermann, 1998; that allows for simultaneous recording of the electrical potential in the xylem with respect to an external electrode (e.g. the TRP) and xylem pressure.…”

Section: The Xylem Ph Probementioning

confidence: 99%

Bicarbonate-Induced Alkalinization of the Xylem Sap in Intact Maize Seedlings as Measured in Situ with a Novel Xylem pH Probe

Wegner¹,

Zimmermann²

2004

Plant Physiology

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In higher plants the pH of the xylem sap plays an important role in drought signaling, growth regulation, and plant nutrition. However, the interpretation of the data is very controversial. The main reason for this is that the xylem pH in intact plants was not directly accessible hitherto. We present here a novel, minimally-invasive probe based on the xylem pressure-potential probe (used for measuring directly xylem pressure and the electrical potential between root xylem sap and medium). Singletipped, double-barreled capillaries were used, one barrel served as H 1 -selective electrode, whereas pressure and electrical potential were recorded by the other one. Upon insertion of the probe into the root xylem of maize (Zea mays) seedlings, pH values ranging between about 4.2 and 4.9 were monitored when the roots were immersed in standard nutrient solution. The pH did not respond to changes in light irradiation (up to 300 mmol m 22 s 21 ), but increased upon exposure of the root to 5 or 20 mM bicarbonate in the bath solution. Changes in pH could also be recorded in transpiring plants when the root was cut below the insertion point of the probe and placed in media with different pH. The data support the hypothesis of Mengel ([1994] Plant Soil 165: 275-283) that upon external supply with bicarbonate Fe is immobilized in the leaf apoplast via changes in xylem pH.

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Simultaneous recording of xylem pressure and trans‐root potential in roots of intact glycophytes using a novel xylem pressure probe technique

Cited by 42 publications

References 71 publications

Diurnal changes in xylem pressure of the hydrated resurrection plant Myrothamnus flabellifolia: evidence for lipid bodies in conducting xylem vessels

Diurnal changes in xylem pressure of the hydrated resurrection plant Myrothamnus flabellifolia: evidence for lipid bodies in conducting xylem vessels

Trans‐root potential, xylem pressure, and root cortical membrane potential of ‘low‐salt’ maize plants as influenced by nitrate and ammonium

Bicarbonate-Induced Alkalinization of the Xylem Sap in Intact Maize Seedlings as Measured in Situ with a Novel Xylem pH Probe

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