Gas and Liquids in Intercellular Spaces of Maize Roots

Michael, W.; Cholodova, V.P.; Ehwald, R.

doi:10.1006/anbo.1998.0964

Cited by 13 publications

(7 citation statements)

References 29 publications

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“…Breaks or fissures of branch roots are difficult to avoid during the manipulation of root systems obtained from hydroculture (Miller, 1987; Fritz et al. , 2010), and pressure application to the root medium might have resulted in infiltration of the formerly gas‐filled intercellular spaces (Michael et al. , 1999).…”

Section: Discussionmentioning

confidence: 99%

“…It was shown that the mannitol translocation to the root xylem and to the shoot of young maize plants can be accurately determined by gas chromatography (GC). To avoid the infiltration of intercellular spaces by pressure application to the root medium (Michael et al. , 1999), the radial water flux was varied by varying the rate of transpiration.…”

Section: Introductionmentioning

confidence: 99%

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Mannitol permeation and radial flow of water in maize roots

Fritz

Ehwald

2010

New Phytologist

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Summary• The postulated nonselective hydraulic route through the root apoplast has not yet been supported by experimental findings on solvent drag.• Therefore, mannitol transport from the medium to the shoot of young maize plants was studied at different rates of transpiration in hydroculture. The concentration of mannitol was determined by gas chromatography.• Mannitol utilization in shoot metabolism was not detectable. Experiments with exuding roots showed that the radial transport of mannitol was mainly apoplastic. The ratio a between the mannitol concentration in xylem vessels and that of the external medium was calculated from mannitol translocation to the shoot or measurement of the mannitol concentration in the root exudate, where it reached c. 0.07 in the steady state. In transpiring plants, a decreased with increasing water flux from 0.04 to values below 0.01. These findings demonstrate that the root reflection coefficient for mannitol is above 0.99.• It is concluded that the radial movement of water to the vessels is under complete protoplastic control, whereas solutes can diffuse on an apoplastic path. The absence of a significant volume flux through the root apoplast is of physiological importance as it prevents the coupling of the apoplastic permeation of ballast solutes, such as NaCl, to transpiration. (ll min )1 per root); a, concentration ratio, quotient between C x and C 0 ; c, fraction of the cell walls in the tissue volume; r, root reflection coefficient for a solute.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mannitol permeation and radial flow of water in maize roots

Fritz

Ehwald

2010

New Phytologist

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“…At insertion of the root into the medium the seal was kept c. 1 cm above the liquid level to connect the aerenchyma of the maternal axis pneumatically with the air space in the chamber. This way the gas pressure in the aerenchyma was kept equal to the pressure on the liquid medium and infiltration of the root cortex at increasing pressure was prevented (Michael, Cholodova & Ehwald ). When the chamber pressure was stepwise increased, sampling of xylem sap was started 15 min after adjusting the respective pressure and lasted 5–20 min, depending on the flow rate.…”

Section: Methodsmentioning

confidence: 99%

Radial transport of salt and water in roots of the common reed (Phragmites australis Trin. ex Steudel)

Fritz

Ehwald

2013

Plant Cell & Environment

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To understand the root function in salt tolerance, radial salt and water transport were studied using reed plants growing in brackish habitat water with an osmotic pressure (pM) of 0.63 MPa. Roots bathed in this medium exuded a xylem sap with NaCl as the major osmolyte and did so even at higher salt concentration (pM up to 1.3 MPa). Exudation was stopped after a small increase of pM (0.26 MPa) using polyethylene glycol 600 as osmolyte. The endodermis of fine lateral roots was found to be the main barrier to radial solute diffusion on an apoplastic path. Apoplastic salt transfer was proven by rapid replacement of stelar Na + by Li + in an isomolar LiCl medium. Water fluxes did not exert a true solvent drag on NaCl. Xylem sap concentrations of NaCl in basal internodes of transpiring culms were more than five times higher than in medial and upper ones. It was concluded that the radial NaCl flux was mainly diffusion through the apoplast, and radial water transport, because of the resistance of the cell wall matrix to convective mass flow, was confined to the symplast. Radial salt permeation in roots reduced the water stress exerted by the brackish medium.

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“…Water uptake by the aerenchymatous main root axis (Michael et al 1999, Lenochová et al 2009) is negligible (Fritz et al 2010). Although in an isolated FLR the local values of Ψ sx may vary along its length, for each FLR there should be an isotonic medium with a defined value of Ψ so that just compensates for the hydraulic effect of Ψ sx .…”

Section: Introductionmentioning

confidence: 99%

Visualisation of xylem sap flow direction in isolated fine lateral roots and estimation of the xylem sap osmotic potential

Fritz¹,

Ehwald²

2012

Biologia plant.

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Xylem sap outflow from fine lateral roots (FLRs) isolated from hydroponically grown young maize (Zea mays L.) plants was visualized by local brightening of test solutions contrasted with purified Indian ink particles. Flow into the vessels was indicated by the adsorption of Evans Blue in their walls. The fraction of the FLRs able to exude xylem sap in a mineral medium with 30 mM mannitol decreased with increasing incubation time. This change was strongly retarded, when the FLRs were incubated in a medium containing glucose instead of mannitol. There was a broad range of variation of the osmotic potential of the test solutions (Ψ so ), wherein the fraction of the FLRs showing an initially reversed flow of the xylem sap varied between zero and unity. A median (M) of the osmotic potential of the xylem sap in FLRs (Ψ sx ) was estimated. It represents the value of Ψ so that was lower than Ψ sx in half of the roots of a sample before their transfer to the test solutions (Ψ sxo ). M was dependent on the osmotic potential of the medium used for growth or pre-incubation of the FLRs. Its value was not dependent on the molecular size of the osmolytes used to adjust Ψ so , including dextran 8, which is excluded from cell walls. In all of the studied plants, M was lower than the osmotic potential of the xylem sap collected from the root before isolation of the FLRs. To explain this finding it is assumed that FLRs with Ψ sxo > M had a higher hydraulic conductivity and a larger volume contributed to the exuded sap than those with Ψ sx < M.

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Gas and Liquids in Intercellular Spaces of Maize Roots

Cited by 13 publications

References 29 publications

Mannitol permeation and radial flow of water in maize roots

Mannitol permeation and radial flow of water in maize roots

Radial transport of salt and water in roots of the common reed (Phragmites australis Trin. ex Steudel)

Visualisation of xylem sap flow direction in isolated fine lateral roots and estimation of the xylem sap osmotic potential

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